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Hopefully we can get you sorted! Definitely sounds like something isn't right.
The first question i would ask is, does the length of time chatting before you get cut off feel the same?
So, do you get cut off at 5 minutes every time or is it just random?
Do both you and your dad have good signal connections? Sometimes a call can be dropped is the signal is low.
Could you also let us know what Network provider you are using. That might help
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