synergy 2150.dial tone problems?

The problem i am having is getting a dial tone. when i want to make a call, i press the green handset symbol and i should hear the dial tone but i hear a bleeping noise similar to engage tone but weaker. The problem is intermittant as i can try a few minutes later and i can get a dial tone. When i get an incoming call its purely by luck if it connects, sometimes it does and sometimes it doesn't.
The base is only one and a half years old.

Can anyone help?