I called back number (07) 3547 7139 reached voice mail but did not say for what company.

Keeps calling then hangs up. Called number from phone booth. Recorded message says they are a charity and that I donated before. But does not name charity

Wanted to get a monthly donation.

called back & says it's a charity but no name given

They call me everyday but I ignore them so far.

like everyone else, I answer call to this number, no one answers back, then they hang up. I'd be buggered if I return their call. It's a scam folks. Just reject the call if they call again. I wish they had Mortein or Baygon that you could digitally spray down the line for these people. They need to be eradicated.

Answered call. Was silent, then they Hung up

Called back number and says it’s for charity that have donated before to or wish to donate.