I work for them - meter bellows are seized and linkages squeek - hence high pitch.
Only ring Transco on 0800 111 999 if you can smell gas.
Since july 12th last year your gas supplier must give transco the approval to change a gas meter. - its called metering separation.
You may be able to have it changed by ringing us direct as having it reported as a "check for safety" but if your gas supplier does not have a metering contract in place we cant change it.
Ring your supplier 1st - unless you can smell gas obviously