home phone billing discrepancies

[#1]

(originally posted in Rants & Raves before I spotted this forum...)
Hi
A couple of times I've been charged extra on my direct debit for phone calls when my credit account had more than enough funds - IIRC, this is only meant to happen if your telephone credit account does not have enough funds or has reached its credit limit. And (I hate to mention it, but...) there have been a couple of 'phantom' top-ups made to my account (not by me) and which do not show up on my transactions list. All very strange.
The last time I raised this question with Plusnet it was dragged out for nearly five months, swapped between Teams A & B whenever the shift changed over, and eventually fizzled out when the billing returned to normal.
Has anyone else had similar problems with their phone billing?
Cheers
Gilbert

[#2]

Your call credit is on a monthly basis.
If you have, for example, on the TalkAnytime package a credit limit of £75 and make £3 worth of calls (taking your credit limit to £72) you will be billed for £3 worth of calls at the end of the month and your limit will be reset to £75.
The only time you won't be charged for calls on your direct debit is if you've manually added to the default credit limit by using a credit card and haven't fallen below the default again, e.g.  added £5 credit to your £75 limit and made £3 worth of calls - you'd still have £77 credit.

[#3]

Thanks for that.
Cheers
Gilbert