[mothered]

Hypothetically if I bought a phone in argos and replaced it with a cheaper version that looks the same when I return it.. The person at the till will probably not know the small details of what the more expensive phone looks like anyway. So I'd assume they would refund me then and there. However what happens then? Are there people in the warehouse afterwards that would report it and would I get away with it if I say it wasn't me?

This does not work.

From experience as of the past few months.

On what grounds was your SE declined?