Open Invoices - changed one name and they alllllll changed.

 Hi all, 

so i ran a sales regiter detail report for open invoice and noticed that one of the invoices had the wrong name on it, I opened that invoice and changed the name and when i went back out, MYOB had applied the name change to allllll of the invoices on that report. 

I have tried going out of the report and just opening a single invoice at a time and changing the names back, but it has done it again and applied the name change to all. 

Any suggestions or guidance please?