Sewerage blockage

After having insurance with them my sewerage developed a problem plumbers were callled out 5 times within 3 weeks each time at a cost of 850.00 they were unable to open the drain and suggested to open up and find the cause. One plumber suggested they would and this had to be done over a weekend as we have a pre school. After a full day of digging the sewerage was under the house. We then made the call and rerouted a new sewerage. The assessor eventually came out inspected after 3 weeks a decision was madeno assistance we reverted the case back to them this ttime legal no assistance. Reason we could not find the problem area