Here's my situation:

I'm a freelancing student and I was working on a software project for a client over the summer holidays of 2010. At the time I completed the application, tested it on my machine, delivered it to the client and went back to University.

However the client is not completely satisfied with the product and apparently has found a couple of bugs with it. Ever since I went back to Uni, they have been chasing me up and asking me to spend some time to fix the bugs. I have explained that this is simply not possible as I am extremely busy with my Uni work and cannot afford to spare my time for anything else.

The client is getting increasingly pissed off and have been chasing me by calling during lectures at evenings and even asking me if I could go over to their place over the weekend to talk about this. This is in turn pissing me off as well because they're essentially asking me to give up my education so that I could help them out by fixing bugs. I go to Uni 5 days a week, 9-6 and feel it is unreasonable for them to call me during evenings and to ask me to work over weekends etc.

I would like to end my relationship with this client but would like to do it amicably without pissing them off. How can I do this? I really wish they would just find someone else but I was charging them piss-poor rates so I think they don't want to go to anyone else because they would have to pay more.

EDIT

The application does not seem to work perfectly on their machine. I had tested it extensively on my machine and it seemed to work fine. I am not sure what exactly is causing it to not work.

I was paid a very low amount and it was on an hourly basis. e.g. I would send an invoice saying I worked on this for x amount of hours and they would pay me for it.

Apart from the work itself, I have not charged them for all the time spent sending e-mails back and forth, phone calls, visits to their place etc. I would really like to end all my dealings with this client right away.