There is no per-access charge for either 1471 or 1571 (just the monthly rental for the latter). It's in BT's tariff guide. I've never been charged for either. Note that in the document below, 1471 usage is explicitly listed as "free" and only callback prices are listed for either number.
So, it's either a misunderstanding or it's a billing error. If the latter, take it up with BT Retail.
Edited by TheEulerID (Thu 13-Mar-14 23:33:33)