Parcel not delivered

I received an sms on the 25th July stating that my parcel was delivered but I had not received the parcel.i immediately contacted the company but they failed to contact the driver and confirm delivery.i have been in contact with the company and their manager Sita promised to look into this matter. It has been over a week and they are giving me the run around. I even wrote an enquiry but still no response. I need to know what happened to my parcel and why are they now ignoring the matter