to be honest in looking further into it and trying to find someone with the same reported fault, there are so many problems and complaints about this, that if it is easy to return I think it might be the best bet.
I have a bt synergy by the way I have a duo set in the office with answer machine and a trio with answer machine at home, they work very well thats why I bought the second set it 's best to stick with what u know lol
I hope u sort it out, maybe try some searching on the web like me typing in the product name in search followed by 'problem and fault' etc maybe you will turn something up..