The problem with fraudulent SMSs and calls, or even telemarketing calls, is Caller ID Spoofing; that is send fake caller ID phone numbers. If you try to call back you get a message telling you that the number does not exist. I don' t know about the UK but here it makes it a waste of time blocking a number because the bar---ds keep changing the numbers they use.
If ever you have wondered why you get calls that stop after a few rings or hang up without response it is because they have a robot caller looking for numbers that are not in use so that they can be used for Caller ID Spoofing.
In an even nastier way Caller ID Spoofing can be used to fake in real numbers for fraudulent reasons.
I don't understand why networks cannot eliminate caller ID spoofing. Here in the UK, BT claim that they will be able to do it when they roll out the next generation network over the next few years.
It should be straightforward. The network allows caller ID creation in support of large corporates using VOIP services with local break out to the PSTN. It should be easy to create a register of legitimate users of this service and bar all others.
