My phone is not charging and its not booting

Hello everyone... Please i need help, am using lumia 550 and it's just a month old. One day, i had a low battery and i forgot to pick my original charger to my workplace, when i got to where am working, my phone switch off and i decided to charge it with a friends charger and i didn't notice it was not charging, after like 30 minute i went to unplug my phone so i could send an email to someone, i tried to boot it but it was still off, that was how i knew my lumia phone is not charging....

I decided to rush down home to pick my original charger, when i plugin the original charger to the phone, the phone vibrated and couldn't on, i now told a friend the problem and he said that i should charge it for like 3-4hours and i did, but was not still charging, i have stayed for a week now without using my phone, please friend what should i do?