A little more info would've been helpful but I managed to find out their website is Euro1Net.com but this is just a trading name for Advanced Data Services (Europe) Limited (trading as Euro1Net) of 78 Queen Street, Ramsgate, Kent CT11 9ER.

A 192.com search for Advanced Data Services reveals a geographical of 01843 580 044.  I would try this number and possibly some nearby numbers.

This assumes that their customer services (and/or tech support) is located at this address.

Their website reveals a freephone of 0800 001 5422 for tech support but is for contract holders only though.