Awaiting a refund for four months now

Hi im honestly upset with the poor service we have experienced with getting a refund from Intercity Xpress, We bought 18 tickets 01 Dec 2025 however we cancelled 1 ticket, we then called to inform all was in order as to how the refund process work days went by in Jan I called again they requested me to send proof of payment along with my banking details which I did send, thereafter no response, I then called in again and so did my mum that when they told us that they working on a month to month process when refunding we understood and wer told we will get the refund end March its not 2nd week April and still nothing.... For such a huge company this is truly unacceptable I mean its now damn 4 months with no services being rendered I DEMAND MY MONEY BACK Zerina ***