Re: TCPA applies
"That's not the case here in the UK however."
In most cases around the world, clearing your voicemail comes off your call allowance and as such _is_ charged (if you go over your allowance it starts costing real money, vs being part of your monthly charge.
That includes the UK.
The thing is, unless it's a scam call they're advertising for someone. That's _why_ the TCPA allows victims to go after the advertiser as well as the company they hired to do the advertising. Follow the money.