Is there any way for customer to restart the conversation ?

I'm using Messaging and our Mobile SDK is connected to our web channel. 

Funny thing is that for those Mobile SDK user , which means they are logged in our mobile-app , they don't get to start a whole new conversation with contents bot menu. 

It's looping for mobile SDK logged in user. 

It's not about setting of keeping the converstation record. 
It does not apply to Mobile SDK users. 

At least, there should be some sort of re-start button within the Messaging. Other wise, they don't receive our greeting message and cannot choose the correct category we have set.