Wedding dress + size 30 I wear a size 24 in clothing Wedding sizing runs smaller

Plus sized formal dress in size 30. I typically wear a size 24 in clothing but wedding sizing runs smaller. Black velvet like fabric on top with a beautiful gold beaded belt sewn on with a royal blue ballroom flared out skirt. From the brand mac duggal. Only work once for a just a few hours Purchased through Marla’s Fashions in Toronto In March of 2021. I paid $640 for the dress and am looking for $350