Keeps calling. No answer

Handy trick; if you pick up a phone call and say nothing, the software at the other end will end the call after 3 seconds (OR you'll start to hear call centre noise - the delay suggesting an international call centre). If you speak then you'll get immediately transferred to a human. Likely to be telemarketer or scam.

I did the above - heard nothing, then after 3 seconds the call was terminated.

If you instead hear noise in the background or you say "hello" after 3 seconds, then there's already a human on the other end of the line.

Wine club sales company seeking to sell their product through an unsolicited call to my mobile.