Hi! I'm Sam, your friendly Samsung Customer Service guy. As for your concern, you may want to check this steps to reset your network:
Hope this helps! Also, if you feel that your sim card is quite old, you may have it changed for free at your nearest service center of your network provider. You'd still keep your same sim card number, they would just upgrade your sim to a more recent one that's more capable in handling network coverages. 😊
