How to force APN hotspot settings to be saved?

Hello,

I need some help, so I have iphone 4 running iOS 7.0.4. The problem is that I can change the APN settings for data and mms, but if I want to set any values in the "Hotspot Tethering" section, for example I want to set the apn to 'online', and I navigate back to 'Mobile' then I want to check my freshly set APN name and guess what 'online' disappeared. This happens to all of the fields if any of the fields are changed/touched which are in the "hotspot tethering" section. Oh and if I only change cellular data and mms section values it is stored nicely... I tried network restore(General -> Restore -> Network Restore), full restore, and even firmware change and then complete full wipe again. And nothing could solve my problem. I hope that someone has already faced this problem and can help me out. I would really appreciate it. Thanks in advance!