... The only possibility that came into my mind is that they have plan to scam the full amount by let op wait and wait until gets bored and forget about the whole matter. This is a classic method used by many services who don't care about their reputation.
Sounds like the usual behavior of shady instant exchanges like Changelly, Freewallet, or even platforms like HitBTC, lol. But let's see, since they’re still responding to the OP in their ANN thread, there’s a chance the issue might get resolved soon.
They are not an instant exchanger, but just a kind of aggregator where everything takes place on their site. Every order is forwarded to one of their liquidity partners (Kucoin, Binance, Whitebit), who further process the swap.
The problem in such cases as the one presented by the OP is that some of the partners require additional AML checks, so everything practically goes through The Change as an intermediary.