Problem with Phone UPC / Chorus

Having being harassed by Chorus for about four months I finally relented about two months ago and signed up for broadband and phone (already had TV with them).
During the two months I have had to call them about five times. People kept telling me when they attempted to ring my number it just rang once and cut off. The phone never rang in the house.
After two visits from “engineers” I was told it was ok. Line test was fine. Today it happened again. Same solution when I rang them “Reboot the Modem”.
I discovered during this time if I rang out from the phone it would clear the problem and would work ok until the following day.
Surely this is some software issue with them and if so what can I do about it?
Anyone else similar problems?

AleoN