Phone [Q] Cannot send text messages (but can receive them)

Samsung Galaxy SII HD LTE
Model: SHV-E120S
Android Version: 4.1.2
Baseband version: SHV-E120S.UJ27.1645.ST
Kernel version:
3.0.31-704944
se.infra@SEP-96 #1
SMP PREEMPT Thu Jan 24 18:32:30 KST 2013
Build number:
E120SKSJMA4-org-mutil

Hi,

I bought this phone recently on ebay. I can see that it's a Korean version (or Chinese?). I run it on Lycamobile (a T-mobile MVNO). And yeah, I am currently residing in USA. I also observed that there is a custom ROM installed on my phone which is named zhibin99. When I try to restart my phone, a console dialog box pops up with a heading "zhibin99 ROM" and it gives me three options to choose from. But all the three option are in Korean or Chinese. So I cannot understand and I never chose any.

Coming to the actual point, I am unable to send text messages. It always says that message sending failed. A week ago, I just changed the proxy settings available on T-mobile's website and suddenly I was able to send text messages but that lasted for a little over 2 days. I got the problem back. Can someone help me overcome this, please?

P.S. I also have some unusual names beside the phone numbers in my call log, such as "FujianQuanzhou", "GuandonFoshan", "FujianNanping", "ShandongHeze", "SichuanBazhonh" and "GuangdongGuanzhou". I'd very thankful if someone can help me with this one too.

Thanks!.