Freelancer has raised an invoice without completion of work

Freelancer has sent me invoice instead of proposal . However my work is not even initiated. once i pay. his invoice am i eligible for a refund ?? Incase of not completing my work ??  Freelamcer says that he cant send a new proposal or create a new gig ?? Is that true. ?? 

I am curious because when i click pay button for the invoice i receive a warning  as below

I confirm that I have received and accepted the work related to this invoice and I agree to complete the payment to the Freelancer.

Kindly help ....