And because a Tesco phone has a UK local dial code eg 01234 xxxxxx, calls to it from BT landlines and from mobiles may well be free if they are using bundled minutes, or on one of the BT options that gives free calls to UK nos (BT option 2 is free at evgs and w/e, BT option 3 is free, always).
Skype In numbers are 056 XXXXX, which will not be free from any mobile or landline, ever.
So, take your Tesco phone, quick call saying "call me back", or an email, "call me at XX time", and it's free for both of you.
