OnePlus Phone review: False promise promos in website

In past two weeks OnePlus Highend phone maker (Competing with IPhone and Samsung) website is giving misleading advertisements to attract customers.

This is a popular Chinese Highend phone maker who sells their phones worldwide including Phones specific to needs in the US.

One Plus Phone website they advertise the following:
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Trade-in Program
Additional $100 promotion value on older OnePlus models.
From Nov. 1 to Nov. 30.
https://www.oneplus.com/event/black-friday-2021
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But when I tried they are giving just $80 for my OnePlus 6T phone.

I contacted customer service and emailed but no response.

I had Similar issue when I tried to purchase a phone that was offered
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Best Price for OnePlus 8T
$300 off, only $449 and get a free Buds Z.
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But when I added to cart the price is changed to $599

In another instance when I added $599 advertised ongoing deal Phone price changed to $729.00.
I am attaching the screenshots of my email communication and their response in this regard.

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