Equipment return problem

I had to terminate my service at the end of April 2017 because we had sold our home and did not have anywhere to relocate the service. I received the box from them on May 9th, packed all equipment in the box and took it to my local UPS office on May 10th. I received confirmation from UPS that the box was left on their dock on May 15th @ 9:30 am. On June 24th I received a notice that my credit card had been billed for the equipment. I contacted Exede and they checked their record and indicated they had received the UPS package and would be issuing a refund. I received a notice on July 24th that a refund had been issued to the credit card but at the same time they rebilled me personally for the same equipment. It is now October 24th and I received a letter from a collection agency that I now owed Exede the original Amount plus a collection fee for the equipment I returned to them on May 15th! I have called them multiple times and am always told that I must wait until they can investigate the issue! What is there to investigate? They have confirmed to me multiple times that UPS left the package with them but they have not updated my account to show that the equipment was returned so a credit cannot be issued! I was told again today that I must wait for them to investigate and they should be issuing a credit in 5 business days. I have very little confidence that this will occur since I have been told the same thing multiple times beginning on June 24th! My next step is to contact my attorney since they are damaging my credit rating! I had no problem paying the termination fees per my contract but I do expect Exede to also live up to their part of the contract and issue a credit for the equipment that was returned to them.