Cancelled Order without notification and calls it system error

I had ordered my  Inspiron 14 7000 Series - 7490 on August 13 2020 and was told the delivery date is 3rd september, 2 days after this I got an update saying the date is updated to 28th september.I was fine with that also and just casually followed up on 29th August and they said it is still 28th september. Today I got a email written without putting any thought to it

@ Dell - Even before I could respond to this mail my order is already cancelled and I was shocked. What surprised me is that the site was still showing this as available but now it is suddenly showing  icore5 for the same price and when i ordered the ad was showing icore7

Please tell me how is Inspiron 15 7000 same as   Inspiron 14 7000 Series - 7490 ?

Is 15 inches and 14 inches laptop same? Is the weight of the laptops same? Is the power consumption same? And this mail implies I either take what you give or get a refund. 

I spent several months researching for the laptop I wanted and then I ordered this.

If I wanted to buy the model  Inspiron 15 7000 I would have done so. I could have waited for 2 months if the reasons were mentioned . This is not reasonable explaination. This is reckless and never expected from Dell. If you dont have stocks in clearance sale then why did you allow this purchase . How can you cancel the order and then ask the customer to pick what you give or take refund. If the order is already cancelled what is the point of this mail and making me wait an entire month . I even followed up with customer care 3 times and latest I followed up on 29th August and even that time i was told to just wait till 28th september.

The order you placed online on 13/08/2020 with Internet Reference Number (IRN) AU***********

This Bundle is originally on clearance sale and now we not able to fulfilled as no longer unit available in stock to complete your order, hence similar model suggested as replacement for your order by product manager which is  Inspiron 15 7000] a 15 inch laptop.

The main difference are = 10th Generation Intel® Core™ i7-10510U Processor (8MB Cache, up to 4.9 GHz)

& NVIDIA® GeForce® MX250 with 2GB GDDR5 graphics memory.

I have also attached a quote for your reference.

 This the only bundle approved by the product manager as a replacement for one off. Delivery within 10 - 14 working days.

 Do let me know your thoughts on this whether you want us to:

 ·         Built the system with the replacement bundle and deliver to you

·         Cancel the order totally and arrange refund

 Hope to hear from you soon and sorry for all the inconvenience caused