Unreachable for enquiries

I have been trying to get hold of them via landlines, whatssup nobody picks up when I call them . I sent a whatssup message and the response was that they are busy they can't assist me at the time and they said they will come back to me , that was a week ago and they haven't contacted me up to this day. I need to query the amount on my statements that I get from them monthly May and June statements reflect the balance that is less and then the July statement hay way bigger bal amount that almost gave me a heart attack. I regret agreeing to deal with this people.