Excel is designed to work with numbers as numbers with a given field length. It will do strange things if you abuse it. It does not handle numbers well as text.
The best way to store the information from the gift cards is in a text file created with a purely text editor that does not support formatting. Windows Notepad, MacOS Textedit both support pure text modes. You can also get pure text editors such as gvim or bbedit for free.
Your statement "Then everything works as Excel should, not as Mr. Gates and his minions implemented it!" is totally incorrect as Excel is working as expected as it is designed to work with numbers.