Verizon Unlocked phone off Ebay?

If i buy a razr off of ebay for verizon (unlocked) and i still want to use my old phone (sch-u740) can I keep my number on both phones? I still like my U740 but I want to take the razr on a trip

can i change the default phone? if you need any details, tell me.
THanks

yes 2 both answers.

u'd hav 2 switch btw. the two as needed