Unkept agreement

My name is MJ Serobanyane a client of ADT since 2008 i called these company concerning my battery which was malfunctioning they came and replaced it.According to the Tax Invoice B 57003 which I signed I was to pay the amount stated on the invoice in two installments but on the 31/10 22 they deducted the whole amount in full.The technician who came to replaced the battery can testify about this.Today I called their office in Bloemfontein concerning this and related the whole whole story but I was promised that someone will call me no feedback so far.