Can I keep my old number with an Iphone 4s?

I currently have an HTC Thunderbolt through verizon and my mother got me an Iphone for christmas. I was on my fathers network but since she got me the phone she put me on her line. It has a number and is all set up but I want to keep my old number. Is that possible?

If it's on the same phone service (ATT, Verizon, Sprint, etc) then you should be able to keep the number. If it's on a different service you may have to change it. That happened with me - my brother got a new phone (but was really for me) so they had to switch the numbers so the new phone had my number instead of his.