A subscriber identity module, or SIM, card is inserted in your phone and identifies you to your cellphone carrier. Generally your SIM card doesn't directly affect how well your cellphone can pick up a signal, but a bad SIM card might prevent you from connecting to the network at all. If you have certain SIM cards, you may not be able to connect to all the services your carrier offers. You can also try a cellphone signal booster if you have bad cellphone reception.
SIM Card and Reception
A SIM card contains an identifier of your cellphone service account and other information about your plan. It's generally provided by your cellphone company when you sign up for service.
Certain SIM cards can be used only with certain types of cellphone service, so a SIM card may be 4G only, 3G only or not include data service. If your SIM card settings don't match your actual plan, this may prevent you from connecting to all the types of service you're paying for. If you're in an area with limited 4G reception and have a 3G-only SIM card or vice versa, this may impact your level of service. If you think this is the case, contact your carrier.
If a SIM card isn't activated, meaning registered for use with your carrier, you may not be able to connect to the network at all.
Damaged SIM Cards
Like other electronics, SIM cards aren't indestructible. If your SIM card gets damaged, you may have intermittent or regular problems connecting to your cellphone network. You may also see an error message on your phone indicating problems with the SIM card.
To keep the SIM card safe, avoid bending it or touching the electrical contacts on it. Make sure to insert it properly according to instructions with the phone or the card itself. Don't get it wet or expose it to extremely hot or cold temperatures.
If you think your SIM card is defective or damaged, contact the carrier for a replacement.
Bad Cellphone Reception
If you're having trouble getting a good signal for calling and texting, or a fast data rate, you may simply have signal issues.This can be caused by physical issues with your cellphone or its built-in antenna or by a weak signal in your location.
You can buy a cellphone signal booster, which will amplify the cellphone signal in your home, or get a device from your carrier, sometimes called a femtocell, that will let you use your cellphone through your home internet connection.
If your cellphone signal suddenly gets much worse, there may be a problem with your phone or your carrier. Contact your carrier for advice in such a case.