1. I need to change my accent to speak right.
Accent is the way a person speaks that reflects their origin.(where they are from) your accent is a part of your identity. It tells a lot about your background and where you have lived most of your life. Our accents reflect in our spoken English. There is a way an Hausa man speaks English and you can easily tell that this person is from the northern part of Nigeria. There is a way an Igbo person speaks that depicts his or her tribe. The Yorubas also have their way of talking and pronouncing words. These are all examples of different accents.  However, some accents are pleasant to the ears while some are horrible to listen to. Which boils down to the need for AN ACCENT REDUCTION TRAINING. A trained English speaker should be able to speak the English language without reflecting their tribe. Note that it is not mandatory for an English speaker to use a British accent while speaking English, because the English language has become a universal language. But At a bearable minimum, he or she should be able to pronounce their words correctly. For example: you should not call "fifty naira" as "pipty naira" because you are an Hausa person. The same goes with every other words. Therefore speaking right means pronouncing your words correctly and applying the stress patterns where needed.

2. If I attended a diction training I would speak right.
Most people believe that if they could just attend a finishing school or diction training programme they would automatically be able to speak right. It does not work that way. You have been speaking in a particular way for over 20 years; for some, over
30, 40, or 50 years, you can not expect all of that thick accent of yours to disappear into the thin air just with a couple of diction lessons. Diction instructors are not magicians.
Speaking right takes a while and also a willing and teachable heart. It also requires conscious effort and constant practice to be able to speak right.
After acquiring the training, you will only be able to speak right by actually making a conscious effort to put into practice what you have learned each time you speak. Speaking right does not jump on people like ripe cherries.
If you don't practice, by speaking; all what you learned in your diction class will remain a mere head knowledge. No one will you ever took some diction lessons because it did not reflect in your speech.

3. I can learn how to speak right on my own.
Some people believe they are very intelligent and can learn anything on their own. So they sit at home and start rehearsing how to speak phonetically.
 If it were that easy, then there will never be a need for a diction trainer. You  will only make little or no progress if you chose to learn on your own. You need someone to put you through.
If you are actually intelligent, it won't take long, your progress will be fast and almost instant when you get a good diction trainer.

4. The white man speaks right.

It is a myth to believe that every white man speaks right. If it were so, Professor Wole Soyinka of a Nigerian descent wouldn't have been tagged as the 3rd best user of the English Language, rated after Shakespeare. Where were all the white folks.
Because someone can speak the Yoruba language for instance does not necessarily mean that you will be able to pass a Yoruba examination, or else there will be no need to study Yoruba in school as a course or subject once you understand the language or grew up in a Yoruba community.
Therefore it is a myth to think that because someone grew up in England or an English speaking country they automatically know the English language better than you. English is a Subject, you know it by studying it. Not by white skin or living in a white man's land. It could help but it is not a fact or yardstick.

5. If I watch movies I will speak right.

This is a serious myth about speaking right.
Movies are written to depict a particular character. The actors try as much as possible to interpret the script by their action/acting. It is not an English learning exercise. Therefore if an actor is interpreting the role of a Scottish born he would try to speak as a Scottish man even if he was an American. There is a high chance of he/she not mimicking the accent correctly. If the movie is about an event that occurred in the 70's or 80's the actors would try to speak and pronounce their words to reflect the time and century as written in the script. If there was a slang in vogue then, they will use such. So you will be copying wrongly if you watch movies to learn English. Watching movies can help you improve on your vocabularies, no doubt about that.

6. A graduate of English knows how to speak right.
In my experience as a Diction coach, I have trained several English graduates on diction and elocution. And I question what they learned in school. Most of these English graduates are familiar with the phonetic symbols, but speaking right takes a personal effort and training not just theories. Most of what the Nigerian University teaches are mere theoretical. That is why a Nigerian graduate of mechanical Engineering can not fix a car, they will still need a local mechanic who did not attend any four walled institution to fix a car.
The mechanic did not read any book on repairing cars, probably he is even an illiterate but what he has practical. Which means he learned by practicing. It is exactly the same with Diction training. Studying English language is theoretical, an effective Diction training is a practical. Putting to practice the things you have learned.

7. If I travelled to Britain I would speak right.
Have you heard most of our footballers speak English, people like Kanu Nwakwo, Jay Jay Okocha, after several years of living and playing in Europe it did not reflect in their spoken English at all. They still speak like people who have lived in Nigeria all their lives. That tells you that speaking right is a conscious effort of the individual not by living in a white man's country.

8. English is not my language so I can never master speaking it rightly.
I am not a Yoruba man but I speak the Yoruba language fluently. So not being an English man is not a yardstick to measure how well one can master the language. I just gave and example of Wole Soyinka who speaks better English than most white men. It is not in the accent or intonation. It is in the expression and usage of words.
It is not my fault that the English language has been declared as our official language in Nigeria and the better you speak it the more likelihood you will be promoted at work or selected to represent your organization.