I had exactly the same experience. Just complained AGAIN on a chat and they gave me half a month refund but cancelled rest of the month. Not the ideal refund or situation but something at least.
This is what I wrote:
'Hey There, I recently subscribed to the sports package solely for the US Open. I am very disappointed with the service and it did not live up to the advertisement. I was wold multiple courts would be available - They weren't! There were minimal 7 minute catch ups from the late night games so missed half of the tournament and last night on the actual final the direct court stream went down after an hour! This is really disappointing and not acceptable for the most expensive sports subscription I have paid for to watch the tennis.'
Surely the worst yet most expensive service for watching tennis.
