Heheh it's my turn to do a scam warning but this one is real and did happen to me honest!
Just got a text from 08700200002 saying "THREE CUSTOMER: Please call ASAP regarding your mobile phone."
Obviously triggered the dodgy flag - looked in google and it seems several are getting this. ICSTIS says:
PhonepayPlus does not regulate this type of number. However we can tell you the following.
* This is classified as a Special Services higher rate: BTs Standard National Call Retail Price for BT customers number.
* It is provided by Invomo Ltd.