Delivery took 25 days and not accepting returns

I place an order on 4/8 and it got delivered on 5/5, that's almost a month.
want to return the product within few days after 5/5, but dell is not allowing it. saying that its over 30 days now. is it my mistake that Dell to almost a month to deliver the product? I called atleast 8 times to talk about it and the customer care is just hanging up the call or just NOT speaking on the other side (on 5/16 i talked to Monika, Suvarna). Suvarna informed her manager will call me in 15 minutes and I never got a call. I am really disappointed with this experience and will NOT be able to come back to buy from Dell in future. Will definitely share my bad experience on my social media platforms.

• 1. Dell Purchase ID:
  2. <Private data removed from public view. DELL-Admin>
• 1. Order Number:
  2. <Private data removed from public view. DELL-Admin>