the credit disappeared within a week of recharge. And it is not like all of your credit disappears, it is more like a large fraction of it disappears, in a way that expiration cannot explain.... And this happened twice to me in the past year. I probably charged 4 or 5 times within a year. So this is not about expiration.
I visited the actual vodafone shop and the explanation was that they cannot provide the details of texts, calls or any transaction for Callya plan, which is the prepaid plan. Are you sure they can see these details for Callya specifically? I can go to a different shop if they can because I totally agree with you, they avoid you if you start speaking English or in general, they don't really care...