Refund of double payments on loan settlement

I have requested the settlement of my loan I was given 20% off .African bank agent set two debits of 3000 and 7 643 they debited 3000 on the 25 November. I called call center and the agent said I must go and pay to the branch I did went to branch later on the same day they debited from my account. I requested for refund I was refunded only 5081 instead of 7740 that I paid in a branch . I logged complains they said they will respond within 7 days still nothing happening