My last samsung phone would randomly disconnect from the mobile network, without any warning, and would keep showing it had signal available.
Of course that meant I would lose calls and texts, because it showed no indication of being effectively offline.
The only fix would be a full reboot.
Which is completely moronic for a brand new and expensive phone. More so if you think that receiving and making calls is the flipping basic purpose of a phone.
I have since then switched to an iphone, using the same sim card and provider, and having no issues so far.
I might go back to android in the future, but surely not to samsung.