T-Mobile prepaid iPhone users?

I'm currently with AT&T and my bill is outrageous. I'm looking for answers from T-Mobile prepaid iPhone users…

Will iMessage be considered a text that you'll have to pay for, incoming and outgoing? Or just like a normal plan because its iMessage to iMessage it doesn't count as a text?

Also, can you still use Wi-Fi with a prepaid phone and not get charged?

Using Imessage would require that you have a data internet connection or Wi-Fi internet. It does not use your text messaging plan. You must have a data internet plan if you have a smartphone (iphone or android cell phone) with any carrier.

On a prepaid using Wi-Fi public hotspots or through your home network Wi-Fi will not count towards your data internet plan by your cell phone carrier. You have unlimited Wi-Fi internet and you will not be charged.