Contractor trying to charge me to finish rain gutters

I had summit roofing do my house roof done a wonderful Job we paid then we decided to have them install rain gutters since they done our roof. They give us our bid to do the gutters we agreed and they came and put gutters on. Before we got bill it rained and a few of the gutters leaked and part of our hous between eves had nothing and was pouring on our deck and some of the down spout extensions were only about a foot long from our basement. I called them said they would come out and take care of problems and they did for the most part we paid bill then got another bill the next month for 300.00 for the extra gutter that was already part of the bid I would assume, when you bid a gutter job it means the entire house. Now what are my choices I told him it wasn't right they were trying to fleece more money from me then 2 months later we got the same bill again what can I do. Signed frustrated