Please contact head offices to complain. By refusing to use self-scan tills out of "principal" you are purely making an already hard job much more difficult at no benefit to either party.
2) If you need help using the till, members of staff will be more than happy to help you if they are not already helping someone else. If they are, patience is a virtue.
I saw a post here earlier today and wanted to share some thoughts, and hopefully open a dialogue about it.
To preface, I worked in retail for over a decade, my partner currently works as a manager for a well-known shop and previously worked as a sales assistant while studying for his accounting degree and master's.
1) Sales staff have no control over the installation of self-scan tills.