Why does my internet cut out when the phone rings?

My phone rings once or twice and then nothing. No internet connection on this line. My cell phone used to

• check home land line phone shows no data after 2 rings. I have had 4 phones on this line for several years with no problems. Connection at phone box OK with 4 rings. I have tried reconnecting wires at split with no success and disconnecting all but one phone but problem remains on all phones. Any suggestions? Jim

• Answer:

  Sounds like 'call-forwarding' may be turned on. I would check that first.