Calls from (020) 4558 XXXX — London
Block (020) 4558 XXXX is allocated by Ofcom to Colt Technology, on the London exchange (allocated 2021).
(020) 4558 XXXX is a number block in London, an area with a population of approximately 9,540,000. Standard landlines in this area use the format 020 4558 1234, with the first part being the dialling code and the rest being the local number.
This block — (020) 4558 XXXX — was allocated by Ofcom to Colt Technology in 2021. Colt Technology either operates the numbers directly or sub-allocates them to resellers and downstream carriers, which is why a single (020) 4558 XXXX prefix can be used by many different organisations. You can verify any allocation against Ofcom's National Telephone Numbering Plan, which is updated weekly.
Some calls from blocks like (020) 4558 XXXX are actually one-ring 'wangiri' calls — the line rings once and disconnects, hoping you'll call back. While wangiri is more common from foreign numbers, UK number-spoofing means (020) 4558 XXXX-style ringbacks are not unheard of. Don't return missed calls from unknown numbers without checking them first.
If a (020) 4558 XXXX number called you and you're not sure who it was, the safest steps are: don't return the call until you've verified it (search the full number online first), don't share personal or financial details, and register the number with the Telephone Preference Service (TPS) if it's a marketing call. Persistent unwanted calls can be reported to Ofcom and the ICO. To block a specific number on most UK mobiles and landlines, you can also enable network-level call screening through your provider.
FAQs about (020) 4558 XXXX
Is (020) 4558 XXXX a real UK phone number?
Yes. (020) 4558 XXXX is part of an Ofcom-allocated UK number block — any number starting with that prefix is a real, dialable UK number assigned by Ofcom to Colt Technology for use on the UK public telephone network.
Who owns the (020) 4558 XXXX number block?
(020) 4558 XXXX is currently allocated to Colt Technology in Ofcom's National Telephone Numbering Plan. The allocated carrier may operate the numbers directly or sub-allocate them to downstream resellers — both arrangements are normal under UK telecoms rules.
Where is a (020) 4558 XXXX number based?
(020) 4558 XXXX is associated with London. UK geographic numbers historically indicated the location of the line, although VoIP services and number-portability rules mean a (020) 4558 XXXX number can technically be used anywhere a CP routes it. For most UK landlines the geographic match still holds.
How do I block calls from (020) 4558 XXXX?
On most UK smartphones, open the recent-calls list, tap the number, and choose 'Block this caller'. UK landlines from BT, Sky, TalkTalk and Virgin Media include free 'BT Call Protect'-style screening you can enable in your provider's app. You can also register your number with the Telephone Preference Service (TPS) at tpsonline.org.uk to opt out of legitimate UK marketing calls.
Other blocks in (020)
Try a different block within the same UK area code:
