Owed Income Tax/ Self Assessment HELP! HMRC

Anyone working in HMRC or an Accountant PLEASE HELP!

Okay so in 2011-2012 I worked at ASDA and this is where the issue has stemmed from, I received a letter from HM Revenue and Customs in April / May 2012 and apparently I owed £329 or something very close to that figure.

So I called the HMRC with UTR number and explained that I couldn't owe this money as they had been taking tax and national insurance via PAYE etc.. the gentleman on the phone then agreed and said he would fix the issue, so I thought brilliant everything has been sorted!

Little did I know at the beginning of this year(2015) in February I received another letter from HM Revenue and Customs stating that I owed them £529 this time for not filling any Self Assessments for the past 3 years, I thought to myself this is absurd as I had started University in September 2012 and I still am (Doing an MEng in Computer Science) and I had only a part time job at Tesco never earning more than £7,000 a year if that!

So I contacted HMRC again and the guy on the phone said "Nope you still owe that money from 2011-2012 and HMRC have put you on Self- Assessment since 2012, failure to complete the Self-Assessment online will be met with server consequence and I advise you fill out that form now" to which I replied "well surely I would of been notified and also I do not have this form" the guy from HMRC replied "Well you've been sent it so I'll have to set up an online Self- Assessment return".

After this I received the relevant details and filled in the Self-Assessment for the 3 years 2011 through to 2014, my next door neighbour is a Practice Junior Accountant so he helped me fill out the online form and an appeal letter as he stated under no circumstances should I have ever been placed on Self-Assessment because I pay any taxes or national insurance through Tesco.

In September I received the most ridiculous letter ever stating I owed the HMRC £13,863.29 with interest of £1.07 a day being added, yeah that right I owe HMRC over £13,000!

I have sent several letters to HMRC as they said nothing can be done over the phone, this morning I received another letter stating that if I do not pay within the coming weeks the bail-lift's will be drafted in to take the full amount.
The fact I do not work any more because of how hard the master year is and that I do not own anything worth or totalling to that sort of money, so now I'm panicking and don't know what to do.

Please help someone? What the hell do I do?

Thank you from a very panicky student.

For you to have a UTR you must have registered as being self employed? If you never registered as being self employed and have a UTR then HMRC have made an error. If your only job has been working for Tesco then you shouldn't have a UTR at all and should not have ever needed to file any self assessment tax returns. Are you sure you never registered i.e filed in an SA1 form?

Sorry the UTR was a from this year I got them mixed up, I just had a tax reference number and my national insurance number on the original letter, as for ever being self employed, never.
I've always worked for someone and paid my taxes where applicable.

The explanation I got from the guy at HMRC if I remembered correctly was because I never replied to the original letter, they thought I was Self employed or I was moon lighting but that's never been the case even when I was an apprentice electrician I paid my tax and NI through PAYE with my employer.

Have HMRC replied to any of the letters you have sent?