12 month deferred interest promotion

I purchased 2 laptops from Dell in June 2024 and a 3rd laptop in October 2024. The first 2 laptops were purchased on a 12 month deferred interest promotion to June 2025 and the 3rd computer was purchased on a 12 month deferred interest promotion to October 2025. I have spoken to 2 escalation managers without any resolve regarding my problem. Dell is saying my promotion  for 3rd laptop ends in June 2025. Being that l purchased the 3rd laptop in October, l should still have 5 months to pay that purchased in full. I have purchased many computers from Dell and l am very disappointed and will no longer be a Dell customer.