u/Ashamed_Economics_31

I got a letter in the mail claiming I owe DHL $31. I get scam texts from them all the time asking for money for my non existing package to deliver.. so this letter made me wonder if it’s a scam. The only package that I recently ordered, I had already received a week ago. I paid for shipping fees and everything, I’ve genuinely no clue with what this is. The phone number is no help either. This seems like a stupid question but I really am confused.