TLDR; SimpleSwap won't send your coins if exchange rates change unfavorably for them, and will hold onto your coins waiting for them to improve in their favor. Otherwise they hold them hostage unless you want to accept fewer coins. Customer service will make up lies as needed.
*I'm posting here because they actively advertise (spam) on this sub regularly, and people have a right to know how they operate.
I recently sent several thousand USD worth of coins to SimpleSwap. They received the coins very quickly, confirmed it, then it was stuck on "exchanging" for hours. 24 hours went by, and I reached out to customer service, who eventually responded to say that it was a "one time technical issue" and that the engineers were working on resolving it. By the second day, they reached back out to say that the problem really was that the exchange rates have changed, and so the transaction had been automatically suspended as a result to protect my funds. SimpleSwap said they'll only be willing to send me fewer coins but not the originally agreed amount.
I replied and said that the new rate only negatively affects them, not me, and that they should send the correct amount of coins as agreed. SimpleSwap then claimed that actually the problem is really that I chose "floating rate" instead of "fixed rate" (which is a lie, I always have chosen fixed rate). This is obviously incorrect as had I chosen floating rate, the transaction would have gone through automatically since it would have made them more money, which itself is the reason I never choose floating rate.
So basically, if rates change, SimpleSwap only send the coin if rates change in their favor, otherwise they won't send you the agreed amount. Here it is over two days later and SimpleSwap still has my coins, and are holding them hostage unless I want to accept fewer coins, and they're making up multiple lies to try and cover themselves.