The one time I dumped a £3 donation via SMS my number was basically call bombed afterwards. After the 15th call in under 24 hours, some at unsociable hours, I took the SIM out and threw it away and signed up for another giffgaff account (I have a few SIMs lying around). This was for one of those "international crisis" ones.

I tend to tell them all to bugger off now. If you're going to shit on me for being nice, I don't want to know.

My mother was a victim as well. Had someone call her all sorts of names for cancelling a direct debit that they'd "miscalculated" on purpose. I managed to get the caller's identity and company and sent a nasty email to their directors. Got a cheque back for the lot. Sod the charity.