MTN useful only when due for upgrades after that its useless

I did an upgrade with MTN last year (2017) June. The upgrade was done telephonically through MTN direct. Lat week (the 4th of June 2018) I called MTN to request a proof of contract, and in that request I clarified that the proof must indicate the date of which I took the contract and when is it ending. They sent a subscriber agreement which is more like an application form. It does not have what I required. I called them back, the told me to call MTN direct. MTN direct sent me to the store I went to 3 MTN stores they told me they cannot help me I must call MTN direct. I called again they told me that they are sending a request to the lady that helped me with an upgrade to give me a call back. It has been a week plus waiting for that call. I even call them everyday but it is useless. I don't understand why they can't help me with at least a letter that confirms that I have contract with them, when it started and when its ending. I need this letter for my work because they are paying for my contract. It is a pity that when you are due for upgrade they everything they can to ensure that you upgrade after that they don't care.