Can you swap sims card with different carriers

You can only swap sim cards if the iPhone is unlocked. i.e it can take sim cards from any carrier.

Regardless of whether its locked or unlocked, it should not reset to the Hello screen (if that's what you mean) when you insert a different sim card.

If the iPhone is not unlocked an you insert a sim card from a different carrier to the one that it is locked to , you should only get an error saying "Sim not Supported"

How to unlock your iPhone for use with a different carrier - Apple Support

StraightTalk phones have a customized activation policy.

You need to discuss this with StaightTalk directly as the situation is specific to that carrier.

Explain what you want to do and see what is needed on the carrier side.

Since this is a carrier's service, you should contact your carriers and they will check your cellular plans / agreements, giving you the appropriate answers.Regards

Giulio