down payments and tenure

I've been with T-Mobile since 1999 have excellent credit. My down payments were the tax portion of total purchase for many years. Now! It's over half of purchase. I've never missed a payment or late on a payment. I have ten lines and, my monthly bill is 710.00. It takes hours to try and get anything done through T-Mobile customer care. I'm getting massage when trying to make an accessory purchase " You can't make accessory purchase online" I left AT&T for less. T-Mobile has a great lip device game. If any other mobile service company come up a Penny less I'll leave T-mobile. Any purchases I use my apple credit card with Apple. 2 years no intrest.