I have verizon galaxy s3 and iphone 4 which both take sim card

[mcrossfield]

can I use my current verizon phones with sim cards on straight talk. Is there anything I would have to do first if so?

 

[hang-the-9]

You need to unlock the phones (contact Verizon for that) and then contact Straight Talk and activate the phones on their network.

 

[Lunatasian]

Yes, you can unlock it and switch to ST. To unlock, just take it into a VZW store, after contract ends, or pay the ETF.