I called back (02) 8318 0207, it was Amplifon (hearing aids).

Calls but doesn't leave message. A few days after I agreed to a charitable giving survey. Regretting agreeing to that survey.

Wouldn't talk and hung up after the second hello.

Annoying and persistent. Ignore

continuous annoying phone call from this number (02) 8318 0207, hung up after saying hello

The call appears to be so short that it doesn't even ring
Possible idea behind this is trigger a "missed call" alert in the hope that:
(a) YOU ring them, thus
(b) Getting YOU on the phone
(c) At YOUR expense

Caller: (02) 8318 0207

Scammer hearing aid company apparently

painfull

Scammer solar panels & the same number twice before with no answer

didn't bother to leave a message

Caller: scammers

report them

Wouldn't talk

Caller: timewasrers

ignore them