Old mutual busy going to my bank and deducting the amount that we didnt agree with. And there customer service line is always nt answered

I have a funeral policy with old mutual which every month my premium is 251 december they never went into my bank to deduct. I went there they told me that i didnt have sufficient funds which was not true. In january they deducted double which i didnt have a problem with as i was behind with 1 premium. I went to old mutual sunnypark to ask if february it will gi back to 251 the lady who always assist says yes february it will go back to normal.To my suprise it deduct 521 my question is where did they get authority to play hide and seek on my bank. There customer service line is not answered and i wont get time to go to the branch. Please help