The answer is NO!
The writer agreed to the contract and is post-facto trying to modify the contract on the basis of Islam’s teachings? Hell NO!
If such after-the-fact conversions were treated as legally valid, everyone would become something as soon as their loans were due - then “convert” back as soon as they could after the loans were paid.
HELL NO!
If we allow this we also need to allow lenders to deny loans to someone who might become muslime and pull this. Watch the liberal heads explode with that!