Tech service charge

We had two techs come out of two separate occasions as our internet was constantly going in and out. The first tech replaced our modem saying that it may fix the problem. The problem was never fixed and we called again and got the second tech to come out who actually fixed the problem stating it was the equipment that was outside our apartment and it had been set up wrong and not only was it affecting us but our neighbors as well. We were charged by the first tech 100$ plus tax for something that was never fixed and was actually an equipment issue on the outside or our apartment that was not only affecting us but our apartment complex. We were never told that we would be charged on either phone call nor by either tech that showed up. Feeling frustrated