OP says it works good on another Phone, if he bought the phone elsewhere it's not M-budget's problem and OP needs to solve this himself. If a setting is wrong it is also his problem.
Sure the desk could help him fix it, but helping him here is already undoable since he does not answer questions about settings.
Apologies, I was away for the weekend. On Friday I wrote to Swisscom for an advise. It seems the issue is the connectivity between Swisscom network and the device itself. Therefore you cannot be certain, it is an issue with the phone as someone indicated above.
Regarding the settings, I did not see any particular question, apologies if I have missed it, however the "proper" settings were several times given to us by the M-Budget support.
When 4G is enabled and Wi-Fi disabled, there is a message saying that the mobile data on this phone has not been activated. According to M-Budget support, there should be nothing to activate, however user omtastat suggested to drop an SMS with message ACTIVATE to 508, which I did yesterday evening. Today morning there was still not internet, however I will wait for full 24 hours. Hopefully there would be a response from Swisscom in the meantime.
I still think you might have more success if you went down into the city and walked your way through a Swisscom shop or two, a MobileZone shop, the shop of your own provider (if not Swisscom, and especially if you can first ask some intelligent question about your own subscription), an Apple shop, and maybe an MElectronics shop.
Somewhere, in one of those, is likely to be a smart young person who works by instinct based on a lot of knowledge, who will be able to punch in a whole lot of options and settings, and come up with the solution.
THANK YOU!!!! I was also experiencing this for the last two months. After multiple calls to M-budget customer service, a visit to M-electronics, a replacement SIM, and a visit to the Apple store, this solved the problem immediately.
Another example of this digital craziness is trying to add a Gmail account to your mail in an iphone. If you have activated 2 factor verification with google then to add a gmail account comes with a " incorrect password message". Und for the average layman one could spend hours trying to sort this one out!