COPY - Poshmark overcharged me shipping on 18 items

I have listed proof of the last 18 items I was overcharged shipping for. Not only did the seller offer a $4.99 discount, but poshmark told me I won a listing contest and my prize was $3.99 shipping and 10% off future purchases. I never received any discounts and was charged nearly $100 in shipping fees and TAXES on some items for some reason! Won’t even bother mentioning the past purchases before holiday shopping! I won’t be listing, selling or buying until POSHMARK makes this right🤬