Poor service all round from PepsiCo

I bought four 2L bottles of Pepsi. I noticed that one bottle has less than 2L by a noticable margin. I complained and it took 3 days for a response. They claimed a courier is to be sent to collect the problematic bottle for what they are calling an investigation. This bottle has been waiting, still sealed for over 10 days now. I have been given no further communications. Turn around is disgraceful here. If these team members are gone on december shut down i cannot be expected to wait for any compensation until mid january