In the UK we have quite a few choices..
With Global Charge/Coulomb I have a 30 minute SMS trial on one of my sites for UK£2. I also use their dialler which can go from US$50 - 250 a month, They also accept Switch and Solo and to be honest.. I didn't think of under 18's using them before I read the post above.. hmmm
And of course good old CCBill now with 900 access for US surfers as well as the usual cc's.
I also bank in the States and have a debit card for my account there and it's a MasterCard which works the same as a credit card, only it's tied to the amount in the bank

I don't know if I have this as I am a non resident account holder or all Americans get this. Do you Americans have/use debit cards ?