You use your mobile phone a lot, so you have large phone bills

A. If you don't use your mobile phone a lot, you don't have large phone bills.

B. If you didn't use your mobile phone a lot, you wouldn't have large phone bills.

C. If you don't use your mobile phone a lot, you won't have large phone bills.

D. If you won't use your mobile phone a lot, you won't have large phone bills.