After several re-writes of our contract (it was rather one-sided on their part), we both agreed on…read morethe invoice and contract details.
Guns N' Hoses added several hundred dollars) to the previously agreed upon invoice, without discussion or disclosure, until after I made the final payment, and told me that my warranty would be invalid if I didn't pay the extra fees. It should be noted that I had already given her several opportunities to discuss any variations, but she dismissed them.
The proprietor, who was friendly until I challenged the additional fees, even so much as swimming in my pool and taking some beer from my premises to give to her team, became insulting and opted not to complete a smaller, but very important part of the contracted job--I had requested that the contract included a clause to attach some wire mesh to a 'squirrel' vulnerable area.
So now, I hear those squirrels scratching away, and have no warranty. I keep asking her to complete the job, and maybe have a conversation to end things more amicably, but she has ignored my requests.