EE SIMs are absolute rubbish. I had 5 non-working replacements sent through the post when one of mine broke, took over a month. So don't order online or over the phone.
Just go instore, it'll take 5 mins, you can test it there and then. It took another 3 SIMs instore before one finally began working! Just make sure you take ID though (drivers licence or passport) as the EE in-store security check that you have to pass is ridiculous! Like Chinese Government ridiculous. Also check your bill the following month, in-store should be free but I was still charged £1.50.
