Some rather obvious suggestions:
Phone land line from mobile, does phone ring, can you answer & talk?
Do you get a dial tone?
(appreciate that on some DECT phones it's difficult to establish this, better with a wired phone)
Substitute phone, preferably with wired phone.
(may be able to borrow from relatives/neighbour if you don't happen to own one)
Try BT line test, 17070, ringback option.
Plug (wired) test phone directly into test socket and repeat tests if dial tone appears.