This could be a network related issue and not necessarily the phone i.e your masts, mast congestion or maybe the sim card is glitching @Claudia1254
Try a soft reboot by turning your phone Off and On and also in Settings, General Management, Reset then reset the network connection.
Their is a diagnostic toggle in your Samsung Members App under GetHelp Section which can check your phone.
Daily Driver > Samsung Galaxy s²⁴ Ultra 512Gb ~ Titanium Black.
The advice I offer is my own and does not represent Samsung’s position.
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