I personally prefer “Service Level Expectation” (SLE) over “Service Level Agreement” (SLA) (SLE is also the term used in the The Kanban Guide for Scrum Teams). I find that the very term SLA dangerously paves the way for focusing on fixed contracts at the expense of customer collaboration which is precisely the opposite of Agile (cf. The Agile Manifesto).
To me there is more realism and authenticity to the term SLE.