Restrict/allow calls from a particular user


Currently as far as I understand using Sendbird Calls SDK I can initiate a call with anybody as long as I know their user id in Sendbird.
That imposes potential security problems and I was wondering if there is an option e.g. to restrict/allow outgoing calls for a particular user?
Obviously a logic like that could be implemented in the app itself, but the things are not so straightforward with the calls when the application is terminated.

Thanks in advance.