Excuse me, how can I set my mobile phone to only receive SMS and not answer the phone?

Call barring of mobile phone includes outgoing call restriction and incoming call restriction. You can freely choose to ban different levels of outgoing calls and all incoming calls, such as banning any outgoing calls and international dialing.

You can set the call barring function in "Call Settings" of the phone "Settings" function. Different mobile phones have different settings. I suggest you consult the mobile phone manual or the mobile phone operator.