Dreams involving ex-partners often reflect unresolved feelings or lingering emotions from past relationships. In your dream, your desire to communicate with your ex-husband's girlfriend suggests a need for closure or clarity about your past relationship, as well as possibly feelings of jealousy or insecurity.

The frustration you experienced in the dream, especially with the inability to hear her and the call dropping, may symbolize feelings of being unheard or misunderstood in your waking life. This could be related to your relationship with your ex or might reflect broader feelings of frustration in your current life situations.

The argument with your mother and the subsequent physical expression of frustration (slapping yourself) indicates a struggle with your emotions, possibly feeling overwhelmed and needing an outlet for your pain. Crying can be a release of pent-up emotions, suggesting that you might need to address feelings of sadness or frustration that you haven't fully processed.

Overall, this dream may be encouraging you to confront your emotions and seek closure, whether that's through communication, self-reflection, or discussing your feelings with someone you trust. Consider what aspects of your past relationships need healing and how you can express those feelings in a constructive way.