I did try asking for a refund, but both the person on the phone and the guy who came to change my meter said that TNB will credit my bill as it is not their policy to refund.
I have no idea how they will credit my bill or re-calculate my bill. I am also curious cause I paid a lot of cash the last 3 months.
Most probably I will wait and see and maybe, after having recorded my usage for a month and no credit to my bill, then I will write to tnb. see how it goes.

Noted. I have kept a daily record of my electricity usage since my first posting. now will keep a record of the new meter as proof.

If not credit by the end of the next billing cycle, then I will start writing letters to tnb and insist on the credit or some form of reimbursement.