Let's first look at the reverse problem, because this is a frequent mistakes in the notebook entries I correct. There are two translations for English "when", "wenn" and "als". You use "wenn" for a condition. Whenever you can use "if" in English instead of "when", the translation should be "wenn". You use "als" for a point in time, when an action happened once, and a second action follows. In this case, you can't replace "when" by "if". German very strictly destinguishes between those two. English "when" can mean both. That's why you can translate German "wenn" both into "when" and "if". In general, you should eventually try to think in the language you are learning, and understand the meaning directly, instead of trying to explain the meaning in a different language. German and English are quite similar, but often enough the meanings and expressions differ.

It is better to understand the meaning of a sentence than a word. Try to get feeling for the word rather than to translate it into English, because translating into English can be confusing. If there is a condition you can translate "wenn" into "if", but if there is time information (temporal) you can translate it ito "when". Are you sure that English "when" is not used in conditional sentences? Now the above sentence contains a condition. It can also be written as: Falls es ein Problem gibt, rufen wir dich an. An example of a temporal sentence with "wenn" is: Wenn ich mit der Arbeit fertig bin, gehe ich ins Bett. (As soon as I finish my work, I'll go to bed)