What if your bank contacts you asking you to phone number supplied in the email what should you do?

If in doubt, check the number by using telephone directory enquiries, look up their number on their website, or ring the bank direct if you know the branch telephone number, or even pay them a visit in person. It is usually okay to phone the number given in the email, but never click on links in the email. And never give any details if asked for your bank account number, and other details - the genuine bank should all ready know such details!