estate settled lawyer verbally agreed on fees but still recieving bills what can I do

[jubes]

What is the name of your state (only U.S. law)? Montana

We settled my fathers estate in 2006 pretty much selling his property. Our lawyer verbally agreed that he would settle our lawyer fees at what they had already recieved (roughly $16,000 from the auction house). The law office cut the checks for each kid in the amount of $10,000 each (3 kids). Now I am still receiving bills from the law office and this is 2 years almost 3 years later! I've spoken with this lawyer a few times and he makes no indication to us oweing more money but I cannot get anything in writting. Last I spoke with him he said we had to sign a book keeping account close form (I can't remember the exact term he used) and that he would send the papers off to us (it's been 4 months still no papers) I sent a letter to him and kept a copy for my self as I knew he wouldn't respond.

I've read that the statute of limitations for Montana on a written contract is 8 years but I'm wondering if this would fall under an Open Account and just be 5 years as the bill is still accumulating interest ( it is at just bellow $10,000).

I really don't want to have to sign anything that's going to say "yes I'm accountable" when I know I am not.