Not really, not like tener que/have to and the similar impersonal hay que/ it is necessary to
que means of course "that" among other things: creo que tengo una teoria/I think (that) I have a theory
Tener que, Hay que http://www.studyspanish.com/lessons/tenque.htm
que between conjugated verb and an infinitive http://www.spanishdict.com/answers/237509/when-to-use-que-between-a-conjugated-verb-form-and-an-infinitive
I believe it's the "personal a", but it was explained to me by a native Spanish speaker that this sentence means we have to call a particular police officer. If we had to make a call to the police in general, i.e., the police station, it would be llamar la policía. Duolingo does not agree at all with this.
Some verbs naturally associate with a preposition. When you use a direct object with the Spanish verb llamar, you need the preposition 'a', so it is "llamar a" + person or thing.
It is NOT the personal a, but the preposition required to llamar. So, addressing alezzix below, if "llama la policia" is correct, then la policia must be the subject and not the direct object. This must be part of a question, because normally the subject would come before the verb.
I think it is a subtle difference. "I have to go to school on time or my teacher gets angry", would probably be Tengo que. "I must obey the traffic laws." would probably be "Debo que". But also I would think that you would find when speaking Spanish in a country or with Spanish speakers from specific areas that they would have customary ways of using these two verbs.