Each time I recharge ,my airtime disappears which made me contact MTN CC.
They inturn told me thatmy call log shows series of calls from an intl line which was surprising because I don't have such calls.That they can't deactivate from there end.

Funny enough I went through my phone and truly theres an intl no there unknown to me.I mistakenly called the no to know who it was(My very big mistake).Infact it has dissapeared too from the call log

How do I deactivate the no cause each time it flashes me which is regular my airtime dissapears .
Has my phone been hacked?