Bill too high

I went from $10 to $107 dollars that’s insane. How. I got the connect more plan that said my bill would be  would be $50 more. I’m expecting to pay $60 my next month. No, they’ve added modem rental and I didn’t even get a new modem I used my own, and something else for almost an additional $50. So from paying $10 to expecting to pay $60 I’m now paying $107. WHAT IS GOING ON? I’m not paying this, I will find something cheaper.