Complex issue- I hope someone can help!

Ok, hopefully I can make myself clear with this. We work with another company that gives us models using their part numbers. I am trying to save the file with OUR part numbers while not affecting the part numbers on their models. I have tried everything that I can think of. I have done "Save as and continue", "Save as and open", and "save as". I have given it a new name, changed all the part numbers in the advanced tab, changed the folder on the right side of the advanced screen to what it needs to be, and when I open the new file, it still references the old numbers. HELP! I have called tech support and this is what they've told me to do. Can someone please HELP?!?!?!

SolidworksGeneral