how can i unlock my iPhone 4s i bought off from eBay and is Verizon im current oversea i want to use a local sim card

Not gonna happen. No USA carrier will unlock and iPhone. For any reason.

can't unless you go to verizon and ask them to do it... must be done domestically

First you'd have to establish service with Verizon. Once a paying customer in good standing, you can then request the GSM portion be unlocked. Obviously, you can't do any of that stuff while you're out of the US. They will not unlock the CDMA side.

Contact Verizon... but let me tell you right now, they won't do it.
Sell the phone and buy a local one or an unlocked one.

You're hosed. Even if Verizon unlocked the GSM side for International roaming, It is completely useless as a phone unless you have active Verizon service.