What are the effects of SMS calling and call forwarding?

At the same time, unreachable call forwarding and SMS call are enabled, and the one that applies for setting first will be invalid; If you apply for unconditional call transfer before opening SMS call, SMS call will be invalid. If you need to use it, you should turn off unconditional call forwarding and restart SMS calling. If you apply for unconditional call transfer after the SMS call is opened, the SMS call is invalid. As long as unconditional call forwarding is turned off, SMS calls can be used, which has no effect on the opening of busy call forwarding and unanswered call forwarding.