Hi Rosie
Apologies for the very late reply - I have been away from this forum but I am not back as a primary moderator. Have you managed to get this issue resolved?
If not, it could be potentially be a problem with filtering - if you have a microfilter connected that is splitting your phone and broabdand connections it may be worth replacing this. You can purchase filters for just a few pounds from most electronic stores, or even the likes of the big supermarket retailers - or alternatively we can send you filters free of charge, but they would take a few days to arrive.
It could also be, as the the above user has suggested, an issue with extensions. If you have extension wiring or are connected to an extension I would advise connecting to the main socket in your premises. If you find it works in the main socket then the extension will likely be at fault, and a local spark could sort that for you.
Regards
Ryan