I purchased a used 7520 (Nextel) on eBay, but it came without a SIM card. Nextel says that I cannot purchase a Blackberry SIM card and that I cannot use a SIM from a different Nextel phone because some of the Blackberry features will not work. Is this correct? Please help

do a search for sim cards here there are numerous upon numerous threads about this. So many that I dont wanna get into the discussion again because there are so many differences. I had same problem as you but others on here disagree with me.

It is correct but it's carrier policy, not a technical reason. Other carriers would be happy for your business.

This is incorrect. Any 32K SIM - grey ones - will work with the BB. Email me and I can help you get set up.

Just make sure its an IDEN sim card