It . . . . . . . . raining since morning when you rang me up.

'Had been' is similar to 'have been' and 'has been', except that it identifies actions that both began and ended in the past. It is used in the past perfect and past perfect progressive tenses. Where 'have been' and 'has been' suggest a past point in time that remains open and unfinished, 'had been' indicates something that is closed and completed.