Go to the Blyk website and click "Company site" near the bottom. Then click contacts and it takes you to this page which gives two addresses:

Member care: Blyk Ltd, PO Box 3026, Stratford upon Avon, CV37 1ZF
Member care tel: +44 (0) 845 702 1021

- and -

51-53 Great Marlborough Street
4th Floor
London W1F 7JT

The first is a PO Box, so it doesn't really exist. May be it is outsourced to another company within the CV37 area.

Anyway, putting the postcode CV37 1ZF into Google leads to this page which gives 020 7220 6348.

It may be that the customer services telephone number is in Stratford upon Avon, so this number won't be there.

Perhaps you could try 020 3206 7600 - it is given under "Advertising", and might be a switchboard number. Even if it isn't, it gives us a starting point for finding the alternative.