Vodacom takes data before expiry

Last Friday evening I purchased a once off, 7 day data deal at 20:30 in the evening. Everything went great throughout the week and worked as it was supposed to. Last night, a week after the purchase I wanted to use the remainder of the data before it expired only to find out that it had already expired. This was just before 5pm. So if at 5pm my data had already been expired, I most definitely didn't get the benefit of a full 7 days of data usage. In fact, Vodacom most probably expired my data at 00:00 on the 7th day. If that is indeed the case I didn't receive 7 days out of that data deal at all, because I lost 20.5 hours worth of usage which means I only got 6 days out. I lost 8 gigs worth of data due to this. Upon complaining about it on their Facebook page, I get a repetitive generic response saying that Ts & Cs state that data expires on the 7th day. I am very aware of this. I'm saying I only got 6 days out of that deal seeing that I lost 20.5 hours of usage which is almost an entire day. So I would expect a refund from Vodacom for not delivering me the full service as they didn't hold up their end of the deal. If no exact time of expiry is indicated, which it isn't, I would expect a full 7 day turnaround, to the very last second! Now I just feel cheated.