How Singtel rewards me for being a loyal customer - to rip $300+ from me!

Long long time ago in my previous compamy, I joined the corporate plan for cheaper Singtel mobile plan. But well, time flies and things change. One day I left the company for my current company. When I was leaving my previous company, I informed the HR to terminate my corporate mobile plan. Time flies and things remain unchanged. After chasing and requesting for a couple of months, my corporate mobile plan was still not terminated. Being too caught up in my current job and too fed up, I gave up requesting to terminate my account.

About 2 years after I left my previous company, I found that my current company is also offering a corporate mobile plan from Singtel. Well, logically since I've already left my previous company and joined this current company, I should change my plan. Also, it was about time for me to change my mobile phone. I went down to the Singtel shop at Citylink and tried to purchase a new mobile phone with a renewed 2 years plan. Then... the counter staff told me that I was not allowed to get a new phone unless I've got an authorised letter from my previous company! I told her patiently that I have left my previous company for the last 2 years and was unable to get any authorisation letter from the company (in fact, the last time that I called, the HR has left the company and the new bird didn't know what to do! omg!). Then the conversation went...

Me: I have left my previous company for the last 2 years and there is no way for me to get any authorisation letter from the company now.
Counter staff: I'm sorry but this is a regulation. I can't allow you to buy a new handset unless you've got an authorisation letter from your previous company.
Me: But I've already left the company! Can't I just switch to my current company's corporate plan?
Counter staff: I'm sorry but this is a regulation. I can't allow you to switch to your new company's corporate plan unless you've got an authorisation letter from your previous company.
Me: Okay fine! In that case, I want to terminate my mobile plan!
Counter staff: I'm sorry but this is a regulation. I can't allow you to terminate your mobile plan unless you've got an authorisation letter from your previous company.

Fed up, I left the shop and dialled 1626. After relating my situation and frustration to the customer service person, and after several calls to and fro, she finally told me that my current company's Singtel account manager will contact me and assist me to switch my corporate plan.

True indeed, my current company's Singtel account manager swiftly contacted me, and after filling a couple of forms, I had successfully transferred my account. Or so I thought.

For 2 months after I've transferred my mobile account, the $300+ that I overpaid in my previous company's mobile account was still THERE!!! I called 1626 again to request help, and here we go again... the same old "we need an authorisation letter from your previous company" story! OMG! So now I've got $300+ stuck in my previous mobile account and there is no way for me to get it back! I requested to speak to the customer service person's manager, and she said that since it is an regulation (AGAIN!), even her manager couldn't help me in this case, but she'll try to get him/her to call me back.

A while later, the customer service person gave me a contact and told me that is the Singtel account manager for my previous company and she should be able to help me. I called this account manager and she requested me to provide her more details via email. Well, I thought that she could really help me... then... one month passed... and... NO EMAIL FROM HER!!! Arghhhhhhh!

Till now, Singtel still owes me $339.02...