Blocked sewerage

The sewerage drain is blocked in my backyard, I have phoned the municipality and eventually they came and unblocked the pipe, just for it to block again two days after. Since then I have phoned numerous times but still no one has come again. It's been two weeks now that all the **** runs out in the backyard. The hole house stinks and no one can go in the backyard. Their service is non-existant. When you phone them all you here is it has been logged, and that's that.