AT&T iPad unlimited data sim works in iPhone 6+, kinda

[T0MMYBOY4]

I noticed a few posts on here asking whether or not an iPad Sim would work in the iPhone 6+. I have the old grandfathered unlimited data plan from AT&T for the iPad, and just tested it on my iPhone 6+ with AT&T. I changed the APN to AT&T broadband as required to make this work. I popped the Sim card into the phone, it said no service for about 10 seconds, and then my signal appeared. Only problem is, I can't get the LTE signal to appear. It will only connect to the HSPA+ "4g" network.... It won't connect to the LTE network. And yes, I get great LTE signal where I am. As I recall reading some other posts on here, people were having the same problem with their iPhone 5 and 5s doing this exact same thing. Does anyone recall what the solution was to get the phone to connect to LTE network with the iPad Sim in the phone?