Burger King Brackenfell not dealing with complaint.

I bought a meal and a shake on 27 January from Burger King, Brackenfell on 27 January 2020. The meal was exceptionally nice as usual but the shake was sour. I logged a complaint with their call center on the same day and did not receive any feedback till today. I called today and they acknowledge the complaint. The consultant said that she will get the branch manager to contact me straight away. It is a few hours later and still no feedback from Burger King. I will not support Burger King again till my complaint has been dealt with in a satisfactory and professional way and I shall ask all my friends and family to do the same.