What company will take action

Hello Friends,

My friend has resigned from the job after giving the two week notice period ,then he got the reply that you have to come up to octmber end otherwise company will take strict action.

he is in probabation period & he confirmed me that he didnt sign any agreement

so guys can any tell me that what are the action will compnay will take.

Company is public limited compnay.

sorry its his life question, thats why i am not sharing company name & my friend name.

Thanks