What kind of phone is it? Does it have have any of the CDMA radios used by Verizon Wireless?
An unlocked GSM phone is not compatible with the Verizon Wireless CDMA network.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
If it's not a Verizon phone, Verizon won't activate it regardless of what technology or frequency it uses, even if it is 100% hardware compatible.