Europcar ai ai ai

i must say that i'm really dissapointed of the service. Iam a loyalty Drive club member for almost a Year and have rented more than 5 cars in the last 4 months ....i retured a Vehicle on sunday, only had a flat tyre (punsher) on the car. i want to book a nother Car for tomorrow on drive club since iam due for a free upgrade ... but iam told that i can't since my other rental hasnt been invoiced yet and they can book a rental but it will not be on drive club meaning i spend 800 rand more for the car i want!!!.... i don't mind paying another deposit ,i have not even received an email to say that my rental has ended like usual i was told that they had a look on the system to see how far the conclution of the previous rental is and aparently they have already fixed the car and 900 will be added for the tyre that should be replaced... i have somewhere to go this weekend but europcar is not allowing me to rent a car on my Drive club promotion this is upsetting and dissapointed