Need help

Last time i opened COD 4 was last month, after 2 weeks i tryed 2 open again and it sad cd-key is in use, i conntacted technical support and they gaved me another code, i tryed that one and still told me that is in use, i conntacted them second time, they sended me another code and it was in use 2 , so please if u have solution or anything that could help me, please tell me, is there any way 2 find any code thats not in use, because conntacting them third time it will give me same results (2 times same thing)
Thanks a lot for any help

Scan your PC for any viruses that may be stealing your keys and passwords and then try a new code. Also, did you contact the official support or did you buy the key off some website and are you asking there?