how do i reset my password when it doesn't recognise my surname and date of birth?

Oh dear, sounds frustrating @Joanne Fenner. 

You’ll need to get in-touch with an iD agent in real-time using the iD Live Chat service.
If the chat doesn't work on your smartphone, then try another device like a tablet, iPad or laptop.

You can also chat to iD Mobile using facebook or Twitter.

Just remember the iD agents work between 9am - 8pm weekdays and 9am - 6pm weekends. Outside these times you’ll get an automated reply.

Good luck!