I wish you all the best my friend, Hope to hear good news. I also like to welcome you to Android Forums.
Thank for the welcome, Javi .
So am update on the issue. I went to the government telecommunications regulatory authority with the phone, box, and receipts. I asked of my phone was registered or not. The person took my phone, dialed *#06# and the imei that came up, he entered into his pc which said registered. He tells me, its registered. So i take my phone and open their own imei checker app, click find out imei, and it shows a different, the original imei, and unregistered. He immediately says, yeah that phone has been tampered with.
They were helpful, to my surprise. Got all the information from me about the shop and said we'll take action cause the law says changing unique identity codes for electronic devices is punishable upto 3 years in jail and told me to take legal action if they don't return it.
I went back to the shop, i told them i was advised to take legal action and to report it to the police immediately. They returned the phone with full payment. I'm glad. I borrowed some cash friends and bought a brand new note9. Wasn't gonna take my chances with a used phone again lol.
Thanks for all the help guys. It would not have been possible without your knowledge and insight of the issue. Thanks Javi.