Lazada made illegal charge to credit card

Two months ago, I bought something from Lazada and everything was good.

Then, this month, I noticed a $28.80 charge by Lazada when I did not buy anything.

On inquiry, I was told it was for membership, and that I could cancel it and Lazada would give me a refund in vouchers.

I immediately cancelled it and requested a full refund.

It has been a week now, and I am still waiting for their response.

Does Lazada have the right to charge my credit card when I did not sign up for anything?

Also, why is the refund being given in vouchers when I am not keen on a membership with them?

If the move towards a cashless society is to succeed, the responsibility of vendors in managing these kinds of transactions is very crucial.