iPhone Recovery Phone Number incorrect

Hopefully someone can help me.  First a bit of history to the problem…..

I provide technical support for and old (94) friend of

mine.  Whilst in hospital recently his

mobile (not apple) packed up.  On release

from hospital we ordered a new phone as his contract was ending.  Unfortunately this had never been

delivered.  After much time and

complaints the delivery agent said they "lost" it.  The mobile agent accepted it had been

stolen.  Another phone was not available

at a price my friend could afford. 

Now, sadly, my friend recently lost his son, and he was sent

his iPhone 6 to use.  This was locked to

his ISP which has now been unlocked.  The

phones been reset but cannot be used as Apple ID verification failed - Locked

for security reasons.  When due process

is followed, I end up having to complete a recovery phone number. 

Here lies the problem; no one who knew his son recognises, or

has a number with the last two digits specified.  I’m stuck. 

Can anyone help or is this a lost cause.

Thanks in anticipation