I'd highly recommend never adding additional services to any account. Adding to the same type seems somewhat ok, but don't do anything that might merge two or more different account types.
After over a decade as a customer I was offered fiber internet which was a lie and I knew it. I previously had no option, but wireless internet. So I figured let them try. Cost me my original account. Apparently when they add something they can't take it away. I lost all of my past login information. Now they've sent an email of my next bill for uninstalled services. The $30 internet offer looks to have hiked my bill about $170 bucks.
If you dare I hope your experiances are better than mine.
I lost unknown revenue from my cell since the loss of my account information to boot. My number was listing funny one customers phones and they were not answering. I would have never known had one not shown me in person.
There use to be a saying the customer is always right. It's not always true, but you should try to respect your customers since without them you'd not have a business!!