personal hotspot name don't change on mac

Here is the thing, I used to have a iPhone 5s till i lost it. So I bought a iPhone 6 and restore the backup of my iPhone 5s to the iPhone 6. I named my iPhone 5s "myName's iPhone", so after I restore the backup to my new iPhone, the iPhone 6's name is "myName's iPhone" too. However, to show the different of those two iPhone, I change my new iPhone's name to "myName's iPhone 6". Yet, when i want to use personal hotspot of my iPhone on mac, it still shows old name, which is "myName's iPhone". Sometimes it worked, I can just click it and connect to my phone, sometimes I have to turn on personal hotspot on my iPhone, and my phone will shows in the list (but not the personal hotspot list, thought the icon of wifi shows a personal hotspot icon), sometimes I have to turn on personal hotspot on my iPhone, and use USB for personal hotspot.

iOS: 8,3

OS X: 10.10.3