Bad charging port. How can I install a new one?

I have bought two charging power supply for my laptop and in a couple of weeks it stopped working both times. I had my laptop for 4 years now but all I can say is that it is my only problem for the past 4 months. Before buying my second power supply I had consulted three technicians and they said it was from the charging cable but I have tried one and it worked fine. I am confused that it seems they did not open up my laptop and saw what the problem is. So I am resorting to your website, I hope you can help me with this. Thank you for your time.