Roto-Rooter Plumbing & Drain Service Seriously exorbitant overcharge for replacing sewer line Atlanta, Georgia

We recently had our sewer line replaced by Roto-Rooter who over charged us the exorbitant amount of $10,000. After the work was done, I contacted  another plumber to get a second opinion. Roto-Rooter over charged us 5-6 times what would have been a reasonable amount. To add insult to injury, Roto-Rooter cut our gas line and has neither fixed it, nor returned my repeated calls. Unfortunately, I signed their agreement to pay via Wells Fargo. What I want is a re-negotiation for a FAIR price to replace the sewer line - not the ridiculously high price they quoted.