How to increase upload limit

Hi guys,
I need to change my current max upload limit (7MB) to 15MB. I got in contact with my hosting provider and here’s its reply:

«The default php.ini we have configured in our system does have a max
upload limit of 7MB. The php.ini settings are universal across our shared hosting environment and cannot be changed.»

I searched my root directory C:\wamp/bin/ and found four files: two php.ini as well as php.ini-development and php.ini-production. I’ve changed them to:

upload_max_filesize = 15M
post_max_size = 15M

I then tried to upload a 12MB file but to no avail. I got the message: max upload file=7MB.

I’d appreciate your help. My knowledge is quite basic, so I’d appreciate it if you could make your reply as detailed as possible.

Thanks!