Landline tested by the engineer and there isn't a problem. Connect a simple handset to the junction box and it works perfectly. Tried to use a more sophisticated device with an answering machine and coudn't dial out when I plugged the device into the power socket, also the dial tone was very quiet. Telephone engineers have twice diagnosed faulty equipment but I tested the second device elsewhere and it worked perfectly. The telephone engineers were at a loss and couldn't diagnose the problem.
Yes
If your phone is mains powered obviously it needs to be plugged into the mains to work correctly , if you haven’t been migrated to DV then the phone ( corded or presumably mains powered cordless phone ) needs to be plugged into the phone socket on the wall ( where the line from outside terminates ) it’s only if on DV the phone plugs into the router , which one gives you dialtone , socket on the wall or home hub phone socket ?
Does your phone with incoming calls and it’s just outgoing calls that don’t work ? , check the phone doesn’t have a signalling switch that can change between LD ( loop disconnect pulses ) and MF ( tone dialing ) , if it does which one is it switched to ? , try switching it over to the other setting.
If an engineer has already been and using their own phone , outgoing calls works, that suggests your own equipment is faulty , although you state it works ok at a different location .
A corded landline phone can be had for less than £10 , or borrow a phone ( preferably a corded one ) from a neighbour, friend or relative and try that ….if another phone works , it’s obvious your original phone , if the new phone also cannot make calls , re report it , but at the moment the evidence is contradictory.
If I plug a simple handset into the BT socket it can make and receive calls. Anything that requires a power plug fails. The telephone engineer couldn't solve the problem and advised using a simple handset. The problem started a few weeks ago when incoming calls on our cordless handsets suffered terrible interference.The engineer came and diagnosed faulty equipment. I replaced the phones but the problem persisted. The engineer returned and said the new phones were faulty. The manageress at Argos initially wouldn't allow a return because she tested them on her system and said they were working. However, she relented and accepted them back. I bought a corded telephone which was no better. A different engineer came and he diagnosed faulty equipment. I have tested it elsewhere and it works satisfactorily. That is the story, so far.
The only thing I can think of that fits with all you've described it a faulty mains socket. That would explain why the phones work elsewhere. Can you run an extension lead from another socket to test if the powered phone works then?