Does divorce occur if the husband swears an oath of divorce that his wife would be divorced if she called him, and then she calls him?

The majority of scholars hold that a divorce oath (halif bi-talāq) effects a divorce if it is violated, whether the intention was to effect a divorce or to threaten. This is the authoritative view (muftā bih). Some scholars, like Ibn Taymiyyah, are of the opinion that the ruling on a divorce oath not intended to suspend divorce, but rather for threat or emphasis, is the same as the ruling on an oath sworn by Allah. Thus, if the oath is violated, an expiation for an oath (kaffārat yamīn) is due, and no divorce occurs. Based on this, since you disobeyed your husband and made the call, a divorce has occurred. If it is not a third divorce, he may take you back (raj'ah) before your waiting period (ʿiddah) expires.