Welcome @rizki27, to the community!
This question has been asked occasionally in the community, e.g. here. You should be able to find further examples using your favourite search engine and e.g. "+stm32 +sip +voip", e.g. there.
However, the features and performance of an STM32F4 will most likely not be sufficient for a VOIP client, which is also mentioned in the above discussions.
Hope that helps?
Regards
/Peter
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