Take it to your dealer for warranty replacement. The dealer should have an agreement with Tecno or their rep which in this case is carlcare. Your dealer should be the one responsible for all warranty issues.
I buy all my devices from Slot because I don't like stories like this. When you buy from authorized dealers, things like replacements are done easily. I cant buy a phone from slot, use for 5 days, it develops a manufacturer defect and you tell me to go to carlcare. Except carlcare is closer to me, I will likely tell you off