Faulty mobile data on 5S

Among other apps, Siri is not working on my mobile data, it works just fine on Wi-Fi. I have an IPhone 5S and live in Romania. Many of us have this problem, as far as I have seen, the issue exists only on an IPhone 5S with a Vodafone sim. I thought, at first, that it is because of Vodafone, but I used my sim with an IPhone 5 and everything worked perfect. Next to Siri on the annoyment scale because of the bugs, it is "Maps" that, again, on the mobile data it is not working properly. I am actually pretty upset about this issue and start wondering if Apple still makes products that worth buying. As far as I have seen with this IPhone 5S I must say that I am very disappointed about the product.