Refusal to exhange baby formula with no explanation!!!

"Refusal to accept exchange of baby formula" On the 14th of December 2018, I purchased a 1.8 kg of Lactogen formula at Pick n Pay uMlazi Mega City. Unfortunately, after consulting with a medical professional, I was advised to change baby formula to another brand. On the 28th December,I went to Pick n Pay uMlazi Mega City where I bought the formula for an exhange. I was told that "they don't exhange" baby formula. I was not given a reason. What ****es me off the most is that there's nothing stipulating this on your return and exhange policy!

When I went to the shop, I had my original till slip and the item was in it's original packaging and still in good condition.

Can I please request assistance on this matter as soon as possible or I'll escalate it further