Mercari They lied to me and stole money when I was trying to sell on their site.

I started the process to sell on Mercari.  I was contacted by a buyer and was told there was an issue with his payment and I needed to contact Mercari.  He gave me the websiteMercari_supportpayment@fastservice.com.  So I did.  They told me that in order to verify my identity and protect buyers from fraudulent sellers I needed to purchase a gift card for min. of 200 and a max of 500.  I know people who sell on there and they never had to jump through these hoops.  I told them I haven't been working and have been on quarantine.  

200 is a lot right now is there another way.  They said it is the rules and it is a new development this year.    It was a onevanilla card.  They assured me it would be given back and deposited right after processing.  So I did.  After it processed they said there was an issue and I needed to extend my credit. They told me I had to purchase another 500 card.   I told them that has nothing to do with verifying my identity.  I told them they are not Amazon and what they are asking is questionable and requested a refund.  First they said they would now they are not responding to any attempt to contact them.