Let us start with one hypothetical.
If you tell the person that you will do so, then you have deceived them. If there is a crowd of people, and you announce that you are calling for help, and then fail to do so then you have put the person at risk by lying. Others will not call for help because they thought you would. Likewise if the person is an employee or a friend or one of your students or a child then you may have a duty of care, but the hypothetical is different here.
The essence of the question is this: do you have a duty of care to a complete stranger? If so, is this duty a moral duty or a legal duty or both? Should someone who refuses to help be charged with a crime? If so, what should the crime be called?
Now let us consider a second hypothetical:
Does change the morality or legality of the situation?
Now let us consider a third hypothetical:
Does the situation change?
And a fourth:
What are your obligations then?
Internal inconsistencies aside, someone's answers to these four hypotheticals tells us most of what we need to know about their fundamental morality.
The libertarians amongst us would say that your only duty to another is to not initiate force against them. Hence you have no obligation to help a stranger.
The humanitarians would say that you have considerable obligation to the stranger - not only responsibility for their life, but for their comfort and possibly even their happiness.
Morality has no objective justification. It is a useful concept because it allows the framework for people to explore common beliefs and values.