Bad luck with my Data?

I have an iPhone 6 and my data hardly has ever worked. I thought it might be my network so I called my customer service and it hardly ever worked for any longer than a few hours so I thought it might be the company or my SIM card so I got a new sim with a new company and it still doesn't work. Thought it might be my SIM card reader but my cousins SIM card worked in my phone and my SIM worked in her phone. Only thing else left to do that I could think of was to call the new companies customer service to reset my network settings and it still didn't work.

Try resetting the apn to default n see if helps