Constant calls and useless customer care

Constant calls and no one can say why

I keep getting calls from 6 in the morning, 21:45 at night, during the day, but when I answer the call gets dropped. Or it rings for a second and then stops

I asked on their supposed whatsapp line, and after being ignored most of the day, (I messaged them when they called at 6:22am and got an answer at 19:10) I am told they use an automated dialler system and they cannot say why I am being called

What is the reason for calling me????????????????????????

Stop with the useless calls