TV Mall ripping people off

I ordered a 50ml bottle of Dr Fuch’s Mimik Relax Face Concentrate Serum on 23 July 2018. It is advertized as a bigger quantity for the same price. I only received a 30 ml bottle. I have tried to speak to a manager Marelyn, but she is never in the office and she never calls me back. Why do they advertize the bigger bottle for the same price as the smaller bottle, but still send the smaller bottle?