Lumia issues

I have always been a NOKIA mobile phone user (except my Sony Ericsson K510) even in this age of Android dominance. The Windows Phones offer me a value proposition which Android phones just can't. But I cant say that I'm not unhappy with NOKIA. 
I bought Lumia 610 in 2012 only to learn that Microsoft was about to introduce Windows Phone 8 which would not be available for my set. I hadn't recovered from the shock when I learnt my Windows Phone 7 software didnt even support USSD which was available since the time the first GSM phones were introduced. Nokia took no step to correct this anomaly even when they introduced WP7.8.
Then, I upgraded to WP8 Lumia 525 as I use USSD heavily. The experience was appreciable until I started having problems of my phone shutting down erratically. After browsing the internet, I saw people using LUMIA 520 complaining about the same problem. People had offered the solution of inserting a small card under the battery in order to improve the battery's connection to the phone.
Now, what I don't understand is, why is Nokia taking such a nonchalant approach to these complaints? If Lumia 520 had this problem, wasn't it Nokia's responsibility to fix it in L525? Nokia should look at their weaknesses if they want to expand in the territory of Android and iPhones.

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Update: Aug 6, 2016

It's deja vu as Microsoft is hell bent on losing the miniscule market share it has left. Just like it didnt update Win Phone 7 mobiles to Windows Phone 8, it has now left many Windows 8.1 phones in the dark when it comes to updating to Windows 10 mobile (including my L525). Although the Redmond firm had states earlier that all W8.1 phones will receive the update, many have been left out.


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Update: July 20, 2019

In hindsight, it is a relief that Microsoft / Nokia stopped manufacturing Lumia phones. Each one I used had a debilitating problem with no solution. A summary is provided below: 

• Lumia 610: No USSD support and was not 
• Lumia 525: Loose battery issue mentioned above. Secondly, it just stopped working and required a change of motherboard / storage
• Lumia 550: Probably the only phone that worked till I disposed it off. Had problems connecting Bluetooth peripherals and did not support the band of 4G my network provided
• Lumia 950xl: Battery issues, phone restarts and blanks out every now and then.