Underweight bags of chips and poor quality

I bought a carton of Lays Lightly salted chips (48 x 36g) and found some of the bags to contain soggy chips even though the expiry date had not been reached. I also found some of the bags to contain only 2 or 3 chips! I reported this to Simba on 22 June by email asking how underweight bags could be released from the production line. I provided the code printed on the bag and advised that I had a sealed packet as evidence of the underweight problem. I received a call a day or two later from someone at Simba with no customer skills who insisted on a postal address to which they could mail me a report. Who still uses the postal service these days? Needless to say nothing has arrived. They are completely indifferent to their consumers!