Max out old credit meters?

Spender£

My elderly relative has those old top up meters with British Gas for Gas (Card) Electric (Key). I heard Martin saying you could potentially max them out before April and pay the old rates as long as they are not smart.
I started doing this a month ago to help her get the numbers up ready but notice BG started taking the credit off the meter and sending it back in the form of cheques!
They sent a letter apologising saying there was an error on their part?
Every time the meter credit goes over £50 on each there is a possibility of receiving a cheque in the post and yet BG told us over the phone the meters can take £240 each or more and they could not explain why they were sending cheques.
Anybody else had this problem?

PennineAcute

It is their way of stopping people using the loophole. 

Spender£

PennineAcute said:

It is their way of stopping people using the loophole. 

I did think that myself however this also happened back in 2016 when She needed to travel to abroad for six months to see her relation, I topped her meters hoping to cover the small amount the fridge/freezer used and She got cheques in the post.
It does seem a convenient way for them to act as a loophole now though and I'm sure the cheques will be on the way. 

wild666

PennineAcute said:

It is their way of stopping people using the loophole. 

That seems the way of not getting customers to build up a large credit balance before April and it could land BG in trouble with the regulator when people who use the loophole to get electric & gas at pre April prices.