Just a little sneaky one ,you also get a link when you sign up to spread the word giff gaff to giff gaff calls are free too so the more friends you get on it the better,my employee is on it so when he rings in sick it doesn't cost him anything but a days wage
Can you keep existing number?
give them a call joe. o2 to o2 you can't keep number on a new contract/sim, only on upgrades, but as it's giffgaff then maybe you can idk. however as mentioned even a no doesn't mean you can't, it's just you have to port it to another netowrk, then back again