Suddenly our Diamond holiday has lost its sparkle

We have paid half the cost of a trip in June but the company has ceased tradingI have just been told that Diamond Rail has ceased trading. I booked a holiday with it in August last year for this June, and paid £579.90 with my card – about half the total and with the balance due shortly. I have rung customer services and just get a recorded message. I have also called Arena Travel which, I gather, has taken it over – but again I get a recorded message giving a different number t