A request from someone you do not know
Decline and block, and stop unwanted requests.
A request from someone you have never dealt with is labelled New contact and comes with a warning. Only go ahead if you know them personally and agreed the loan together.
Decline and block
Under the request, open "I do not know this person, or did not agree this loan". Tick the box to report it to us if you like, and press Decline and block. They cannot send you another request or agreement.
Stop requests altogether
In Settings → Requests & Blocks, choose Only people I have dealt with or Nobody.
People who are refused see the same neutral message whatever the reason, so they cannot tell whether they were blocked.