T-mobile T-mobile charged for "Premium Services" without my knowledge or consent and won't give full refund. Internet

For a few months I received occasional short text messages from Mobi-spin on my T-mobile phone. I finally checked our bill and saw that we were being charged $19.98 per month for this. We never requested these services and were never told about them. T-mobile responded that it is up to us to check our bill for these charges and up to us to block our account from charges such as these. They could only refund 45 days worth of these charges, a small fraction of the total. T-mobile receives payments from scam companies such as Mobi-spin, so they are in no hurry to let their customers know that their accounts are not initially blocked from scammers, and not willing to refund the entire amount of the fraudulent charges. Take warning if you have a cell phone account.