[ADC]

Had a nokia N73 on contract for about 4 months and everything has been fine. But over the last week at about 12-12.30 every day when i'm at work the signal vanishes. Its OK before that time and the signal returns when i get home. Removing the battery and sim and replacing them make no difference at all. A work colleague is also having a similar issue with his N80 from the same network.
Am I within my rights to cancel my contract as it is not fit for purpose. I don't see why i should pay for something that doesn't work when i need it.
The network are currently investigating the issue BTW.
Thanks in advance people