without a phone number displayed are difficult but these scams are named as a bank, pay pal, and the post office.
If you have a number you can report it on 7726, also "Amazon" and "DPD" are still at it. There is a web site called "who has called me" so please check,and don't press any button options. Its your hard earned money these scum bags are after. If you do get a voice call,keep them on the phone and it then gives others a chance of not being scammed .