Any experience with tellows call blocker service

Hi
I have recently switched to voip/sogea with Fritz 7530 router. Plan was to plug by BT8500 (2014 vintage) advanced call blocker dect system into the analog port on fritzbox. Call blocking is erratic and weired faults (eg 999 call fails). I see truecall now advise unsuitable for use with voip. I have found german company tellows.co.uk advertise a software product that specifically works with Fritzbox. Only reviews i can find are from Germany. Has anyone any experience of how effective their blacklist is in UK or make other suggestions. My old BT8500 predates GAP so suspect I am in the market for new handsets as well.

I am not a fan of black lists (as you imply, they may not be up to date, tellows I think is community maintained so you take what you get) & I liked the challenge / response of functionality of the TrueCall. But having recently moved to VOIP using a Fritz!Box (not Zen VOIP but that is irrelevant, I think) I found a workaround that is a bit clumsy but so far has not caused any problems.

I imported all my Contact details from my Apple address book to the Fritz!Box.

This created a new Address Book which I had to copy into the main Address Book on the Fritz!Box.

I then created two diversions directed to Voicemail:
- one for any anonymous callers or no CLI
- the other for any phone number not in my Address Book

Quite clumsy (& one needs to maintain the Address Book either manually or by repeating the above process - but my contacts change infrequently now I'm retired) so I have sent a Feature Request to AVM to implement a more elegant solution.

The main downside is for legitimate callers who either withhold their numbers or whose numbers are not known to me - the NHS is an example. If I am expecting such a call I disable the Diverts, just in case they do not leave a message.

Having said all the above, we get very few nuisance calls (we kept our geographic telephone code) & I don't think any failed legitimate calls.

If anyone knows a better way then please say !