Poor service delivery

On the 28 April 2019 my father opened a case against his 5 people who are siblings of his wife , they attacked him at home. beat him up and we opened a case of assault against them, only one person was arrested and was out on bail. The other 4 have not been arrested and nothing is happening against them. Detective Mbiza never made contact was so ever to us as family or my father to this date. Then Detective Kili took over the case and promised to look for them and do arrests until today no arrest has been made . I as the first born of my father tried to contact Langa police station on numerous occasion without success. Today I finally spoke to Detective Kili who told me the case is going back to detective Mbiza , can I please get assisttance to ensure the police take this case seriously and the 4 people need to be arrested asap two are working in Grooter Schuur hospital and the other at UCT both dectetives has contact numbers of the people but have never made an effort to even fetch them from work whatsoever case number is CAS279/4/2019

Langa police station number is *** Station commander :*** Branch Commander :***