Can i put an at&t iphone on a verizon plan?

I'll jailbreak it so of its jailbroken can I switch the carriers

No.AT&T and Verizon use different kinds of technology for their phones and towers.

Jail-breaking doesn't let IU switch carries it lets you use 3rd party apps and what not, you would have to unlock the phone but like he said, att uses simcards and verizon has some computer thing that switches contacts and what not.

Unlocking and jailbreaking iphones are not same process.Jailbreaking is helps remove the restriction in the i-phones to accept thrid party applications, software, music etc. In Many unlocking method jailbreaking is must before unlocking i-phones.
Unlocking helps to removes the network lock. If you delete the network lock in your i-phone you can use any network in that phone. You can jailbreak your i-phone using the site www.iclarified.com/jailbreak/
So after Jailbreak your i-phone you can't use with other network. Unlocking only makes the i-phone to accept other network sim.
But you can unlock I-Phone from AT&T USA Network lock. After unlock it you can't use with Verizon it's CDMA. You can unlock GSM Network locked phone and use with GSM Network. To unlock i-phone use remote unlock service is best than software and other unlocking tools. Software is very big unlocking method. So i would suggest remote unlock method. It is very simple method. In this method you no need to jailbreak i-phone compulsory, you can unlock it and then you can jailbreak it. To buy remote unlock service for APPLE I-PHONE, visit the site http://www.theunlockspot.com/apple-iphone/rs10wp9/ buy remote unlock service and unlock it easily.