Advice:
Make sure you check the amount sent to your account before releasing the coin. But not only that, make sure it is the right amount because the scammers are sending an amount similar to (but lesser than) the amount that you are expecting to receive.
This scam is common and many of us are neglecting it and it is becoming rampant everyday.
This advice of checking the amount been sent for you before you release your coin is very important so that if the money is not complete you can chat the vendor for your balance and give negative anonymous reviews; but if you do mistake and release the coin before noticing the incomplete amount of money because even if you chat the scammer, they will not reply you.
The best thing to do now is to always verify the exact amount been sent to you before releasing your coin, you can as well send the money to another account to be sure of the money you received before releasing the coin.