Phone socket replacement
If it's your only socket it should be a master and replaceable with an Openreach Linebox.
https://www.youtube.com/watch?v=jbfHMsP6IsE
https://www.ebay.co.uk/itm/NTE5C/254283763063
Note - if you do want Openreach to replace it for you, you'll have to book that through your phone provider (whether that's BT, Talktalk, Sky, Plusnet etc) as Openreach don't deal with consumers.
If it's an extension socket, just replace it with a LJU 2/3A.
https://www.ebay.co.uk/itm/BT-Socket-LJU2-3A-/221531118698
For that you will need an IDC insertion tool (included by that seller)
Details on UK telephone wiring (and how to tell the difference between master and extension sockets)
http://www.rob-r.co.uk/other/UKphonecatwiring.htm