Cannot Get Rid of Them

I called and received help from this company, now I cannot get them from continually calling me!!! I have asked to be taken off their call list and they just will not do it. 1-800-423-6492 is their no., Mark Webber is the guy that keeps calling and he says I must be at my computer so they can give me credit?? Sounds fishy to me. He says they are authorized Microsoft repair reps but I am not so sure now. If they cannot send a check and they need access to my computer to give me credit, no way. I want them to STOP CALLING. They have called about 15 times now - what is so hard about, keep the money and remove me from the call list!!!