If you're not happy with the product; hold the Mastering guy accountable.

If the mastering engineer doesn't say "no problem," loads the files, reverses the channels, then re-saves, you might consider a new mastering engineer. Just make sure something in your system isn't reversed first, either in terms of record or playback.
 
A lot depends on what the engineer is doing but if the end result is a disk image or DDP file, it's easy to reverse the channels in just about any DAW or digital audio editing program.

I would still strongly recommend first to talk to the guy who did it and find out what happened in case something else unpredictable crops up later. It may seem like a simple fix as others have explained, and it probably is but don't get caught out (in case of other problems that might have not been seen yet).
 
If he supplied an ISO image for a CD it may well need to be rebuilt (if there are cross fades between tracks then it gets more complex).
 
Toby has the right idea, but be nice everybody makes stupid mistakes... :)
If he/she is untouchable and unapproachable then I agree with Craig, I know you can get some drama queens who can take things far too much on a personal level (blinding them somewhat), rather than want do the right thing...
 
Cheers.
 
 

If the channel switch occurred before the ME applied other distortions another reverse pan may sound off. Things like widening reverb and delays and other fxs may become phasey skewed or jumbled ... I do not know.

It's not going to mess anything up, reverb or otherwise, just by reversing the channels. It's no different to wearing your headphones back to front or simply facing away from you monitors.

First, verify that it's not you that has something reversed. It's easy to accidentally swap cables when tidying up or reconfiguring your rig. Plug some headphones into your interface and verify that the mains are wired the same way as what you hear in the headphones.
 
Once you've determined that you don't have a problem with your own setup, re-read Craig's answer. The ME should have offered to reverse it for you at no charge.

first, I really don't no how to post that the problem or inquirer has been solved, I would appreciate anyone telling me how to do that, because I have asked a lot of questions here over the years.
second, now that is out of the way. I want to thank everyone who responded to my problem and told me how to fix it.
right now I'm half way through the project but needed to say thanks.
the channel tools plug in is exactly what I needed. ****ing brilliant, works great. the next thing i'll do is contact the mastering studio and informs  him he has some wires crossed.
again, thank you to everyone and have a happy Christmas.
joey pinter    

Hi Joey, just edit your first post and change the title to include [Solved] or [Answered] or [Fixed] whatever it appropriate.
 
I'll do it for you this once.  Just this once mind...  no special favours in future

Leave all cables connected as they are.
Don't mess with anything in software
Take the right side speaker and move it to the position of the left one
Take the left one and move it to the position of the right one
 
Done... problem solved