I bought some stocks through DBS Vickers using cash upfront. Recently, I sold the same stocks through DBS Vickers too but my brokerage account balance shows negative. Did I do something wrong?

I sold through Cash option as that was the only one available. However the next day, when I open my DBS app, I realised it shows a negative amount to my brokerage acc. I’ve emailed DBS Vickers but there hasn’t been a reply. And today I saw the negative amount increasing as the stock price climbs. I buy and sell the stock through the same brokerage acc. Did I do smt wrong? I’m panicking so badly right now 😭