Hello my 3 landline phones sometimes ring and then incoming calls sometimes do not ring but one phone sometimes gives a slight ring. Also I can call out no problems. No computers or modems installed.
Any ideas would be a great help before I have to call the phone company and pay for a service charge.

Better than 90% of the time I see this, it is a coroded jack and/or line cord. Look inside each jack, then try with 1 phone and the other 2 unplugged, then try a different phone with the other 2 unplugged.

First, verify that you can receive incoming calls with a phone plugged into the Network Interface Device (NID) outside.