My question involves collection proceedings in the State of: Washington

I've been paying our medical bills every month through a set agreement amount, which comes out as direct debit from my bank account. Today I received 7 letters from this medical company saying that it's our final notice. Pay up or go to Collections. Nothing was said about the amount we were paying when I called a little over a month ago and updated some information. Now they want more money a month or we're going to collections. Can they do this?

So frustrated!

Susan