Budget Air co uk - Refund not transferred

I had booked a flight ticket via BudgetAir on Dec *th **** and they couldnt process it with the airline.
BudgetAir claims that they have refunded the amount on Dec **nd ****, but are just not sharing a valid transaction reference number.
Instead, inspite of my repeated emails, they are asking me to share my bank statement as proof of non-receipt, which is invasion of customer privacy.

Inspite of repeated emails, their useless, non competent customer service team, is asking me to check with my bank on the refund but how can I do so, without any valid proof of transaction from BudgetAir.

This has been going on for more than a month now. Apart from an email ID, their customer service team is not even sharing any contact details of their management team and not returning my money too