what is the problem

my phone battery drops from 50% to 0%

Replace battery.

Meffi NV. What answer are u expecting? Tukuambie ni sim card?
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Fanya hivi nunua simu ingine na uache kusumbua. We unataka kukufa na simu moja tu

kwani inadrop ka suruari

Jaribu factory reset
Ikipersist nunua simu mpya