Do you have caller ID as a part of your package with Virgin. With some landline phone providers it is automatic but with Virgin you have to ask as it is an extra service. It comes with an extra charge of £2.25 per month or so, could be less if it is negotiated as a part of your overall package. If you have already asked for it and it is not working properly then phone 150 and make inquiries.
i assumed that the OP had caller ID. call guardian cannot work without that to tell it who is calling.
but once caller ID is in place you set rules for how you want various types of calls to be handled, as per the user guide.
e.g. our rules are that VIPs ( family) can call anytime. other calls are muted from midnight to 6am, then we have a list of allowed callers ( friends, contacts) who are never challenged, a list of blocked callers who are not allowed at all. and another rule that says if you withhold your number then go talk to our answering machine. anyone else gets to run the gauntlet of call guardian politely saying state your name and business in order to be let through
once they are through, it's one button to add to either the allowed, or the blocked lists for next time
if I need a callback from ,say, amazon, I can go in and temporarily turn call guardian OFF, else it blocks the robo calls
my only downside was initial confusion over how to allow local landline numbers, Despite some of the on-line advice, what we had to do was store the 6 digit number, only without the local 012xx prefix, then it works.
it is a shame that caller display is not free, I recall one poster claiming he got it free as a special deal but it's not free for me.
from memory, it can be enabled over the phone , and takes effect almost immediately