Sprint refuses to refund an overpayment once I cancelled my long distance

I recently canceled my long distance account as I do not use it any more and they are claiming I cannot receive the $150 credit on my account since it is non-refundable.

Here is the gist of the problem.

Last fall my roommate made calls home to Sweden and racked up an impressive $250+ bill for only a few minutes since the effective rate was something like $2-5 a minute.

Once I received the bill I called sprint and they were more than willing to adjust the bill and put me on an INTL plan as I had never had this issue before. That was nice of them.

This re-rate took 3 weeks and in the meantime I had to pay the bill to avoid late fees. They said I would then get the credit back since their payment system does not allow partial payments online.

A few months later I realized no one had used the phone in 2 months, so I called to cancel and get my refund. Unforetunately, this credit back can not be given as a refund despite them saying it could.

Next I asked who can fix this. They claimed "research" could look at it, but only offered a fax number and I have had no response. In addition, they need to receive the data back from research, but they claim they don't coordinate with them. They said they could not contact research directly either.

I am very confused as this is an overpayment that they are claiming in non-refundable. I refrained from getting upset at this and politely moved up the supervisor chain. I believe it was the Florida call center. Despite conversations, I was unable to get any help.

Sprint lost me as a PCS subscriber who paid close to $120 a month for 6 years because they were not responsive. This is even more ridiculous.