I think this needs some summimg up.
If you have a normal phone line running to the home and that line terminates anywhere in the home[and is activated],then when you order infinity they send out an HH3 router.
That router should arrive about 2 days before the engineer comes to fit infinity.
He should bring an OR modem with him and make the exciisting socket or any socket a master [using data lines if needed].
The engineer was obviously lazy or unskilled.
It is just a normal infinity install that should not have been a problem.
Contact the mods on this forum and ask them to get it sorted out.