Unable to send text after unlocking iPhone from EE to o2

[Tabs]

I have been given an iPhone 7 Plus which was locked to EE but is now unlocked. I put in my new o2 sim everything works except I can’t send normal text messages and also when I downloaded whats app it tells my contacts that I am not on what’s app? I think there is something wrong with the internal settings in the phone not changing to o2 properly from EE?

[MI5]

@Tabs 

Check your number in Settings >Phone >My number and correct it if wrong.

[Tabs]

Thank you for your reply. The number is correct

[MI5]

@Tabs 

Did you factory reset the phone first before putting your SIM in? 

Are you correctly logged into iCloud etc?

[Tabs]

Yes I reset the phone to factory settings, also did all software updates. I am correctly logged into iCloud

[MI5]

@Tabs 

Assuming you have "send as sms" turned on, I'd be inclined to back up to iTunes and factory reset again.

[Tabs]

Yes sms is turned on. I have factory set the iPhone several times but still not working. I think maybe there is a problem with the message centre number for 02 maybe it has not changed from EE. Does anyone know how to check this and how to change it? I tried typing *#5005*7672# on the keypad but it did not work? Thanks

[MI5]

@Tabs 

That is the correct number but you'll need to turn off wifi calling to send it.

On the phone keypad type in *#5005*7672# - this tells you the message centre number installed in the handset.
PAYG should show : +447802092035  Monthly : +447802000332
If it doesn't, type in the sequence below.
##5005*7672# this deletes the message centre number.
Then **5005*7672*+447802092035# (for PAYG customers)

or **5005*7672*+447802000332#   (for pay monthly)

[Tabs]

I tried the above number to find message centre number but it says Unknown error dismiss. Is there another way to find out message centre number, I am using iPhone 7 Plus thanks

[MI5]

Did you turn off wifi calling first?