Who should pay for poor signal strength

I had issues with 1-5 drops in the 1-3 min range and dozens of drops in the second range so i called COX. All my equipment and wiring was OK but signal level was poor so the tech installed a drop amp and now they charge me $75 for it?   I would think COX is responsible for the signal strength at my incoming line?  Anyone that has experience with this? C.ustomer service claims it is my responsibility.   I could agree if there used to be an amp and I unplugged it but in this case there is just a straight connection to my modem.