when you block a number, it is blocked permanently. I think these unwanted calls are coming from spoofed numbers that keep changing. by that, you have just blocked 01234 000000, but the same spoofer has set up their dialler so that the next time they call, it is a 'new' number (01234 000001, for example). you now have to also block this new number, ad infinitum. I think it would be better if it was possible to block a string of numbers (all calls originating from the 01234 prefix, for example), but I don't know if there is a specific app for that.