Handset Troubleshooting (No signal and other network concerns)

• My phone isn’t connecting to my mobile internet. How do I fix this?
• My phone isn’t receiving any text messages. What should I do?
• What should I do if my phone can’t send text messages?
• My phone has a problem with receiving phone calls. How could I fix this?
• I can’t make calls to other number. How would I fix this?
• What should I do if my phone isn’t getting any cellular signal?