Simple vs Continuous in the Past Tense and in the Future Tense

Even though I understand the difference between the simple and the continuous aspect of the English tense system, I sometimes struggle to understand what each of these two aspects expresses in some past and future contexts. Let me give you two examples:

1a. When I was a teenager I sometimes called my father.

1b. When I was a teenager I sometimes was calling my father.

2a. This is the last time we are seeing each other. I will sometimes call you.

2b. This is the last time we are seeing each other. I will be sometimes calling you.

I get the meaning expressed by the past simple and the future simple in the above example sentences but I`m not feeling the continuous. Could you tell me what meaning does the continuous aspect convey in those?