As explained by englishpage.com, using the past continuous "was ringing" here would imply that the person had been ringing prior to 2 o'clock and was still doing so when 2 o'clock arrived. This is obviously not the case, which is why you use the past simple "rang".

Did the phone ring or rang?

To answer the original question, "rang" is the past tense of "ring", and "rung" is used as the past participle form of the verb.

Is was rang correct?

4 Answers. Today, was rang is considered a non-standard form since the accepted past participle of ring is rung.