Even the manager doesn't help

I lodged a complaint against a staff member for not getting back to me within the time that he said he would. This was done about 3 weeks ago. On 28 October, the store manager, Suzette, called me to say she'll discuss the issue with the relevant staff member the next day as he was not in that day. It has been nearly 3 weeks since we spoke and I haven't received any feedback, no phone call, not even an SMS. So what's the use of escalating the matter to management if the store managers don't even do anything to help serve their customers? How do I escalate the matter further?<br>