Refusal to honour warranty

When I initially bought a dishwasher in 2018, I emailed their Customer Service to enquire how to register the product to qualify for an additional year's warranty. I received an email to say there was no need to register it as the product carries a four-year warranty regardless of what the manual said. Now that I need to have the dishwasher fixed, the Customer Service Agents insist that it only holds a two-year warranty despite the email they sent in 2018. The agent said the person who emailed me was dismissed. Hisense still has to honour the promised four-year warranty regardless of the in-house issues that have no bearing on the terms of agreement amongst them and myself.