If dig safe didn't mark it correctly, then they own the problem. If you don't call in advance, then the error is on you. My electrical and cable lines are 6 feet down in schedule 40 electrical conduit. At 2' there is plastic warning tape in the ground, and also at 4'. There should have been warning tape above the lines that you snagged. Whomever installed them, went cheap and omitted the warning tape. Most likely an independent contractor for the cable company.