Why is my phone flasing all the time and it shows extension in use, and I can't make a call ,?

Question

I have at&t landphone model 5840

Answer 1

Try unplugging all the phones from all the jacks and just fix oen phone in the demarcation jack and see if you have a dial tone , if you dont have contact your service provider

if you have a dial tone on the demaraction point

see if you have a fax machine or anyother machine is connected to the same line and if it is use

or see if there is any problem with your hand set.

Answer 2

if u have no dial tone on ne of your phones, try to unplug them and plug back in after about 5 mins (inplug from electrical for crdlesses too.) If this doesnt work, you want to plug a phone in at your telephone network interface device. If you have no dial tone there, that means its a outside trouble and the phone co. will fix free of charge. If u do have a dial tone there, its an inside trouble and if u dont have inside wiring insurance they will bill you. (Verizon charges 91$ 1st 30 mins and 46$ each additional.) Good luck