You can wait until you can pay or they will - but they should pay. Keep on them and read your policy. Or, you can also choose to do nothing at all.
I have waited 2 yrs now because of infections, but I will be getting the ball rolling again in Sept.
There is a Federal mandate if the surgery is for the diagnosis of breast cancer insurance companies has to pay there is no statute of limitation. If later you need a revision of the surgery that will be covered too.
My insurance company sends yearly reminders that I can have reconstruction surgery from lumpectomy in 1995.