Is MMS messaging free with unlimited SMS text messaging with a T-Mobile iPhone?

I have unlimited texting(SMS) and I just recently turned on my picture text messages (MMS) settings for my iPhone. I was wondering if I have to pay for MMS for every incoming or outcoming pic, or does it count as unlimited texting too?

Added (1). I pay for my internet too, if that helps with anything: P

If it doesn't specify it in your plan, then probably not. But it will use up your data plan quite fast if you send MMS texts a lot, so be careful!