Call Analyzer can help you count the total call duration and warn before reaching a specified monthly limit. It records all your outgoing calls and gives you summary and statistics about total call duration, number of calls, most frequent number etc.
It also shows a call breakdown chart for selected dates.
A warning can be set for a specific limit of monthly minutes. The warning can be shown when starting and/or finishing a call as well as notification, sound and vibration. All settings are configurable.
There is also an ignore list where selected numbers can be added to, so the application will ignore them when calculating the total call duration.

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