Hotel-Spider is the best if you ask me
Possible solution is to set the double and single occupancy prices in the Booking Extranet to both be manual, not automatic, and set up your Channel Manager to send the prices per occupancy level that you want, if you have more options in your Channel Manager.
If you cannot reach the propery support, you can try to call the public customer support. They can normally redirect you to the property support department.
Perhaps compromise with the guest to agree on charging 50% or only the 1st night.
Either the guests are being less than honest to save money (and we don't want to fully reward that) or there was some kind of misunderstanding.
Time is money. Don't spend too much time and stress on this in any case. If your card company is warning you about disadvantage and this is a big disadvantage, then maybe let them win...
Going great for us. We have around 60% of Booking reservations from Genius guests and are in the top 20 best-selling hotels in our city.
But be careful in regards to protecting your direct rates. Genius discounts will accumulate with ALL promotions and will affect ALL rate plans that you have or create. The genius discount will apply at minimum to your lowest room type.
If you want to be "fair" to some other partners, carefully calculate that if you for example give Expedia 10% additional Members discount on to a 20% promotion, the Members promotion will be 30%. Therefore to create an equal Members Promotion on Expedia you would set the discount for the Members Promotion to 28% and the Public Promotion to 20%, as the Genius price would be €100 - 20% promotion - 10% genius = €72. Easy mistake is to give Expedia a €70 promotional sell rate by clicking the standard options ;).
If you already offer a 10% direct reservation bonus or something similar, and you want to increase your volume of Booking reservations, it's a very good possibility when combined with lifting your BAR rates a little in my opinion... but there's basically no going back after you go Genius... and your competitors may follow you!