When I worked there we were closely monitored on the amount of credit we gave away and in trouble if it was deemed too much. For that reason if someone was querying credit that hadn't been given, I would also refer back to the original person offering it and ask them to add the credit onto the account. Daft I know but you had to look after yourself and that £30 could be the difference between making or breaking your stats
Things may have changed so this could be old, duff info so don't take it as what may be happening nowadays.