Check the router is set to an 'Always on' connection and not 'On demand'.
If you have ADSL try changing the ADSL Micro Filter, the most common cause of intermittent connections is a faulty filter. If you have FTTC please skip this step.
Please insure that you change the RJ-11 lead between the microfilter/FTTC faceplace and the router/modem.
Make sure your router is connected to the BT Master Socket and no telephone extension leads are used between the wall and the router. Only use the supplied modem cable directly into the BT master socket.
You can also try disconnecting any additional devices connected to the phone line such as fax machines, Sky Box, Red Care alarm, Credit Card terminal/Paying Device, telephone extension leads, etc. to avoid any possible interferences coming from these devices.
Swap the router out for a replacement.
Noises on the telephone line can cause disconnections in the broadband signal. In order to identify if this is the case please try a Quiet Line Test.
Connect only a phone, preferably a corded one, directly to the phone socket and dial 17070. It is recommended that you disconnect all devices from the line, such as ADSL routers, phones, faxes, credit card terminals, Sky Boxes and alarm systems.
Once prompted, select option 2, and then observe the line for any cracklings, noises, interferences or clicks.
If you do hear noises on the line, please contact the line provider and inform them that your line is experiencing high noise on the line and this is affecting your broadband signal.
If you are still experiencing disconnects after carrying out the above checks please contact the support department to carry out further fault diagnostics on the line.
It may require an engineer visit to resolve the issue, therefore it is important to carry out the above checks to rule out any equipment faults on site. Any engineer visits that do not find a fault within the provider network are chargeable.