Re: I bought a $15.00 (100M) data plan, but I can't use it with my iphone 4s
There is a special workaround to get the data plan to work. Unfortunately, those types of things cannot be discussed here. I will give you a hint, though: you have the change your iPhone's APN settings.
If you are successful at changing the settings, the data plan you purchased will work. Until then, you are out $15 for something you cannot use.