Try calling SE and ask them if you COS (change of supply) read is correct and confirm the MSN with them for your gas.

Also give them all the digits on your meter so they can see if it is 4 or 5 dial meter, all the number, points and numbers in black or red.

They should do a usage checklist with you and if there is a problem with the meter they will fit a type of test meter to check.

If they do all of this and it come back that that is your usage there isnt alot more you can do.

You have to be paitent as it may take a while as SE dont own the gas meters its transco so they have to book app with them.

Stick with and you will get it resolved!