when you save £3 and lose £1000s instead

On Monday I went to this pub nearby where I live as they were listed for the Eat Out to Help Out scheme on the government website. The government guidelines clearly state that if you participate you must offer 50% off on all applicable sales (that is food and drinks, excluding alcohol). When I got my bill, to my surprise they did not apply the discount to soft drinks. When I questioned this the poor young waitress first replied she didn't know why, then said they were too busy to apply it to soft drinks as well. There was no point discussing this with the waitress as she clearly was out of her depth. And also it was only a £3.10 discount we are talking about. But sometimes is the principle that counts. I felt misled as they are listed on the government website which will clearly give them some extra traffic. I sent them a message on Facebook and basically they replied that they would rather do it only on food rather than not do it at all and that I should have informed myself before going. Now I want you to think about the following points as all of us, sooner or later, will face this situation:

1. Offering the discount on drinks doesn't cost them anything
In my case they gave me a hand written receipt, discounted the food and could have discounted the drinks in another 5 seconds

2. If there is some important information that can affect our customers we should communicate it at the first possible chance, in this case when I made the reservation. (or for instance when something is missing on our menu, when presenting the menu, rather than when taking the order)

3. We can't just reply to a complaint in a dismissive manner without showing any sort of empathy
Expecting me to know about this was just naive. Also they did not make any extra money on me, but I lost £3.10, and because of how this was left I will never go back again (also the food was below average, but this is another story) so they have lost thousands of pounds in potential future revenues

4. You should make a difference between internal issues and customers issues.
What I mean by this is if we have a problem internally (lack of technology in this case) we shouldn't automatically assume that our customers will understand this and be sympathetic. Even as a small business we should try and move with the times. Adopt new technologies. In their case I imagine they could not program their point of sales system, but also if they have a POS, why wouldn't you print receipts from it rather than write everything by hand again? Puzzling

5. For everyone that mentions there was something wrong with their meal, there are another 10 that don't say anything and just won't come back. Mind that won't say anything to you but they will tell their story to another 8 people (real stats) or worse put it on Facebook or TripAdvisor.
When I worked in the corporate world someone coined the term "Feed Forward" (rather than feedback), as feedback helps us improve and move forward. I love good, honest, constructive feedback as if our own customers don't tell us where we went wrong how are we ever going to improve? Without feedback and criticism we risk resting on our laurels.