Septic tank not emptied completely job not well done

After 2 years that we stay at this property the septic tank was full and we got Teloc waste management to come and empty our Septic tank paid R1500 for the call out and a moth later the septic tank is full again ,it takes approximately 3 to 5 years for the tack to be full,I did contact them and told them that the tank is full a moth later and they told me that their guys will not leave unless the tank was completely empty and for them to come back we need to pay again R1500 and to me it's a ******* as per the plumbers we had here to come and unblock the main line to the septic tank, they told us that the tank is full and that they can't do anything till it is emptied .Telcloc waste management refuse to come back unless we pay them again we will never make use of their service again