So what should i do? How do i get my £669.60 back? Should i take legal action against Thameslink?
Well I think a "Letter before action" would be a sensible next step. However, before you do I would advise you to be certain that your story is 100% factual. If it did get as far as court then you would need to be able to support your arguments.
There are a lot of circumstances in this story which on their own may not raise an eyebrow but combined, become a set of coincidences all happening on one journey which certainly would raise questions.
We have a customer who appears to have arrived at the station with their five friends but would appear not to have checked in advance the train times.
We have an inept customer assistant who sells a ticket to a station where there are two of the same name.
We have an employee who commits a criminal act by stealing £120, or we have an impostor who manages to have a uniform and ticket issuing equipment.
We have a customer who carried £700+ on him/her.
We have a customer who doesn't seem to question why the original tickets were very expensive and hands over £400+ for the tickets.
We have a customer who hands over £120 and doesn't seem to have an issue (at the time) with not being given a receipt.
All of these are of course possible, but you must realise that together they seem unusual and quite coincidental.
Other things seem unusual.
How did the group get from the platform to the ticket office at Luton station without a valid ticket.
Was there no discussion at Luton ticket office about the case when the second set of tickets were being purchased.
Did you not raise it with at least one other employee on the day?
Where are the tickets? You haven't mentioned what has happened to them.
Are you willing to share some/all of the emails you have sent/received? They may help others be able to advise you better.