FATCA - change of classification

We advise the trustees of a trust where the assets were originally invested by a discretionary manager. As such the trust was classified as a FI. The trust was registered for FATCA and a trustee dealt with the reporting.
The assets have subsequently been moved to an execution only investment manager and as such the trust no longer qualifies as an FI.
Presumably we now need to deregister the trust from FATCA. Does anyone know anything about how to do this? I have found some (minimal) information online about deregistration on the termination of a trust but this is not quite the situation here. Thank you.