At this point you call them, threaten to leave, and they find a new "promotion" that resets you to baseline and the process starts anew. I've gone through this with them for the past 10+ years. Their latest trick is charging for any usage over 1.5TB (which is criminally low if you have kids streaming, playing, and talking to friends all day IMO), but instead of tacking on one of their overagew bundles (which are somewhat resonably priced) they charge a huge per-GB fee.
I'm about 2 blocks outside the primary service area of a large suburb so they're my only wired option that provides at least 100MB down speed so I'm stuck with them.