Lg defects on tv

I purchase a LG oled TV and was told by the LG representative this is the best tv and we will have no issues. This TV is now giving us a message to call LG to change the power board cause in other countries this model is frying up. They want to send a technician to my house to fit the new power board. I have tried to call LG so many times and lefy messages for them to call me they never did. Two weeks I'm calling with no joy. The manager call me today to say they will replace the power board but if anything happens to the TV after that they not responsible. I'm says I paid a lot of money for a brand new TV not a repaired TV so it's best if LG give me a letter to say they will be responsible for any future defects on the TV for 48 months of replace the TV. I didn't ask to sold a TV with defective parts. I am very unhappy with LG and there poor service. Please can someone assist.