Amazon India — the product isn't delivered on time even after continuously following up from 24 hours

Hi,

I have ordered one plus 7 with a guaranteed delivery date of 31st aug, 19 and the same hasn't been delivered yet, even after following up from last 12 hours, nobody is even bothering to deliver it on time. Even the delivery executive and members from amazon delivery center are talking very abruptly, i have called the delivery executive atleast 25 times, after disconnecting 24 calls, he picked the 25th call just to say he is on leave, and without even listening to me he disconnected the call. If he was on leave then why the package was assigned to him?
Is this the guarantee amazon is giving to a prime member? This is the worst experience i have ever faced, i won't recommend amazon anymore. It is really disappointing for me.