my phone is stuck on 1% !!!

Hi everyone, so today I was out in London and it was very hot, and I had my phone in my hand most of the day. I go to Costa and plug my charger in to charge up my phone and my battery won't go up in % and instead goes down. My two friends tried the charger in their phones and it worked perfectly (one of my friend's phones went up 5% in 2 minutes!!) So as I thought, my phone turned off after reaching 1% and when I got home, I tried a different charger and as I sadly thought, my phone is stuck on 1%... someone help!!