like something an actor might do?
cause I say it does make sense and is a perfectly fine phrase.
That accent isn’t real; he is effecting it.
and my friend says it is wrong
who is right?
Either you are, which I agree with, or everything I grew up reading that used that very phrase was wrong.
I see nothing at all wrong, or even odd, about the phrase.
It should be “affect an accent”, that is to put it on.
Affect is something you put on or have
effect is a result
Right, and doing it regularly is an affectation 
I’m pretty sure this is an occasion where effect is appropriate as a verb.
You’re wrong.
dictionary.com defines affect as:
2.
to assume artificially, pretentiously, or for effect: to affect a Southern accent.
Hm. That seems kinda weird.
I thought this was going to be all about spelling and now I find it’s all about vocabulary. Your spelling sucks and I feel cheated.
You are wrong. To effect is to put into action (she effected fundamental reforms when she took over the company) , to affect is to put on temporarily for effect (she affected an accent to please her in-laws).
I would imagine the reason for “affect” (which I’ve always understood to be the correct usage in this context) is that you’re changing the timbre/pitch/cadence of your voice, which in most cases does already exist, i.e. it’s not so much that the accent itself is new, it’s that your voice is a constant and you’re modifying your voice.
That, too.
You affect the accent to get the effect of an accent.
Unless you want to effect a flat affect in which case you’d have to effectively affect the tone of your voice for the effect.
Yup, you “affect” an accent when you put it on as an affectation. To “effect” an accent you would have to bring the accent about all by yourself, which is going some; most of us have all we can do to effect a change in the pronunciation of a single word in the language.
To affect an effect, effect an affect.
That’s what I always say.
In this case, affect would be correct.
Certainly, “affect an accent” is more familiar, but if one is putting a particular accent into action, then arguably one is effecting it as well as affecting it, at least if one is successful. I don’t think it has to be a new accent; to successfully carry off an existing accent would be to effect it. Effectively.
Effecting an accent is what happens to, say, Brits who live in the U.S. for a while. Constantly being surrounded by people who speak differently causes an effect on their accent.
And after seeing “accent”, “effect”, and “affect” so many times all three words are losing meaning.
Now that the OP has been addressed, I would quibble with the suggestion that you might in fact say “effect an accent”. Effect, to my mind, means to bring about some circumstance or make some event or series of events happen. An accent is not a circumstance or an event, it is just a thing. So it sounds wrong to say that you could “effect” one.