Calling a Web API from a stored procedure in the RDS hosted MSSQL Server

A lot of stored procedure in the migrated database called a web API to process complicated data. However, during the RDS migration, we are only given "admin" user with limited access causing some of the Stored Procedures to fail.

The EXECUTE permission was denied on the object 'sp_OACReate', database 'mssqlsystemsource',schema 'sys'.

I've done a lot of google search, unfortunately none provided a concrete solution. Can anybody guide us on how to solve this issue?

Thank you in advance ;-)