Phone went on dead mode after battery change after working fine for 1h

My phone went on dead mode in 2017 and was not even getting switched on even when i kept it for charging. replaced the battery of the phone by myself by following the instructions from the company I purchased the battery. It was successful as phone started to charge again and was switched on and was working all good. Suddenly it stopped charging after 70% and I was updating the phone with the latest software. As soon as software was updated the phone went off and was unable to switch on again. Its not charging either . I tried to reset or reboot by pressing the hone and power on button together for 20 seconds. But nothing happened. I feel that apples software doesn’t let the old iphones to work smoothly or work at all so that people can buy new ones.