TravelUp complaint: Misspelt passenger name

Booking Ref: TH1719259. Flights were booked and it was noticed that one of the passengers names was misspelt. The name Allan was spelt Alllan (an extra L) A phone call was made within 24 hrs and they requested an email. A reply to the email was given as follows: As you booked tickets on 15/01/2023 and sent an email 17/01/2023 which was out of the 24 hour window. We responded on 19/01/2023, please note the name cannot be corrected as ther are 2 different airlines booked. you need to get to the airport 3 hours prior to the flights time to check if they can let you board with an extra letter. I have been through both the airline with who the flights are with, they are all with British Airways, and Travel Up several times and they keep bouncing us between them.British airways state they cannot change a Travel agents booking. We are at a loss as to how to move forward