Prestashop customer upload file

Hello, I need a Prestashop Expert to help me out. I have a website which needs to allow a customer to upload a file, with a maximum size of 15mb with there order, there seems to be an issue which Prestashop do not seem to be able to fix with the built in function which causes the following to be displayed "Fatal error: Out of memory (allocated 173277184) (tried to allocate 20736 bytes) in /home/sites/###########.[login to view URL] on line 238" I have already tried the obvious, [login to view URL] and .htaccess No matter what file i try to upload the same issue occurs. Having spent hours searching the internet I have found no help, so it you think you can help please bid.