Not too sure if we was just lucky, but we never got charged anything when we had a broken wire in the copper pair killing our phone, however our broadband was fine, but slower but worked.
We phoned BT via one of our mobiles and had our line redirected to that, I did ask if we would be charged for this redirection where I was told no due to it was a fault their end.
We received several calls that was redirected, some lasting several mins each, and we never received any extra bill.
So like I said we may of been lucky, maybe they caused the break due to I was told the break was either near the PCP cabinet or in it and where our PCP cabinet is one of those really old cast iron ones and all the cables inside is like spaghetti junction it would be very easy to break or knock out a wire.
*** update ***
Ooops, didn't read the OP fully, wasn't aware of the allowance, we just used our free call time on our mobiles.
Edited by PaulKirby (Mon 09-Nov-15 05:30:06)