It's not their fault that your transaction took over 12 hours or 24 hours without getting confirmed. Next time learn to use higher fees if you want a quick purchase.
It wasn't the fact that OP used a low fee here that was the issue. The issue is that the transaction he made was spending an unconfirmed input.
It is not safe to accept a zero confirmation transaction with an unconfirmed input due to transaction malleability. Let's say I make transaction A which sends 0.1 BTC to address 1XXX, and then make transaction B which sends that 0.1 BTC from address 1XXX to BitRefill. Both transaction are unconfirmed. Due to transaction malleability, transaction A (after being broadcast, but before being confirmed), could be changed by a node or a miner in such as way that while the signature remains valid, and the transaction itself remains valid, the hash of the transaction changes. This does not make a difference to transaction A - it will still confirm normally. It does, however, make a different to transaction B. Transaction B knows which input to spend because it uses the hash of transaction A. If the hash of transaction A changes, then transaction B becomes invalid.
Even if transaction B had a huge fee of 1000 sats/vbyte, it could still effectively be cancelled due to the malleability of transaction A, and that's why BitRefill needed to wait for 1 confirmation.
As others have said, this is not a scam and is entirely down to OP's misunderstanding.