Disappointing and pathetic GMAT experience

I took the real GMAT on 21st Aug 2019 at Pearson VUE center in Bengaluru

Exact Address :
No 45, 3rd Floor, Trade Center, Dickenson Road Above Bhima Jewellers, Bengaluru, Karnataka 560042.

The registration process was smooth but the test experience after that was horrible. There was a person taking the GMAT sitting beside me who started the test at the same time but was coughing so loudly throughout the test and was continously murmuring the questions he was trying to solve.
I could somehow manage the Quant section but comprehending long sentences in Verbal was near to impossible due to his constant coughing and murmuring of questions. I even informed the invigilators sitting outside the test room during the 8 minute break about this issue. But there was no effect. I tried wearing the noise-cancelling headphones given but they were very uncomfortable.
I ultimately spoilt my GMAT and scored a disappointing 660 ( Q51 , V27 ).

My official GMAT mock scores were :

1) Mock 1 - 690 ( Q50 , V32 )
2) Mock 2 - 700 ( Q50 , V32 )
3) Mock 3 ( Took after spending 2 weeks on SC ) - 750 ( Q51 , V39 )
4) Mock 4 ( 4 days after Mock 3 ) - 740 ( Q50 , V39 )
5) Mock 5 ( 2 days after Mock 4 ) - 740 ( Q50 , V39 )

I raised a issue after the test and also raised an enquiry through mba.com portal but I have not got any reply from GMAC yet. This is very disappointing that GMAT test centres dont maintain a calm environment for test takers.