Disgusting customer service, it's gives promotions without complete information and cheats the customers with partial information

It’s been n number of times that I have faced such issues. Completely my mistake that even then I tried orders the products but now I am done. I am writing this only to make people aware of the fraud mechanisms they use to grab customers attention and compel us to buy products from them even if we do not wish to.
As mentioned, I have faced several issues here are a few of them.
I tried purchasing one plus 6 a couple of months ago, my phone was crashed and I was awaitingy interview call so placed the order for next day delivery and to my surprise on the day of delivery, the executive came to my home and entered incorrect IMEI number in the devise while delivery and said " I am sorry Ma’m I have entered the number incorrectly and I cannot deliver the item. The device will not allow me to enter the number for next for hours so I shall get back to you by evening and deliver the product" . I said ok and he never turned up. He went back and cancelled my order. when I called the customer service, the representative said the order has been cancelled and we can’t help me I am sorry but please place another order. Because of them I couldn’t attend my interview call.
A month ago again I saw the one plus 6 t promotional NB add and pre-booked the phone after going through the terms and conditions. According to which if the customer pre-owned books the phone, they’ll get a headset free. I went ahead and pre-owned booked it. When I was trying to place an order today, it wasn’t accepting the code. I called the customer service and they said the pre-approval booking is not applicable on orders that are placed on EMI ( which was no where mentioned on the promotional site). So I will neither the headset nor I can use that pre-owned booking amount for placing the order. When I got that escalated, the supervisor just had only one thing to say that " Sorry madam, we should have mentioned that pre-booking offers are not valid on EMI facility, completely our mistake but we can’t help you. All you can do is place a fresh order and you can use this pre-owned booking amount to buy something else from our site" .
This is how these people are cheating us. We in a perception that we’d get a benefit of pre-booking placed and order and the end we are fooled and compelled to buy the products from their store.
One of the pathetic online store that is cheating the customers without their notice in every possible way.