adt/nbs dont care

on the 20th March i received an sms from that i should take advantage of the easter special and pay R876 and get a R424 discount instead, being excited i called them the on the 26th to really confirm i was then told that the sms was sent error and the correct will follow while we are talking on the line, the sms now says R967.20 and the "easter special line " is included in the sms, i then asked the consultant why it has increased she just said my manager says this one is correct, cool on the 26th march 2018 i made a payment of R967.00 did not include the .20 cent on the 12 April 2018 i get a call from creditworks/nbs that i owe adt account for R500 because i did pay the .20 cent , i asked why did you not contact me within easter coz i made a payment on the 26th easter finished on the 02 april ? they reply to say sorry mam but our system shows that balance and when are you going to pay.- really for just 20 cents , im willing to ;'paying 20 cent not R500 you are taking chances nbs