Double check that you have the password correct. It's on a card on the back of the router https://www.plus.net/help/broadband/router-user-guides/
Note it is case sensitive and make sure you aren't confusing zero and O, also one and lower case L
If that doesn't help, is your phone only capable of 2.4ghz ?
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
