Spend limit that didn't ask for

On the 7 June I received an SMS that my usage limit has changed from 2.00 to 118.00 which I emmediately declined changing it back to 2.00 but on the 31 July when I got to the store to pay was told I'm owing 650.00 which I don't know and asked the lady why and she said it's my spend limit and I said I didn't apply for that and she said there's nothing she can do I have to pay the money or else mtn will close my account and I paid the 530 I know which I pay every month.on the 13 July I received same SMS that state that service provider made changes to your usage limit therefore can your account not incur any out bundle cost which again I declined to 0.00 from 118.00.i went to the store to fix this several times and was told I'm have to pay or call the mtn call centre which I was told to speak to the billing account which I don't know and 7 August 2023 u woke up to my service been closed and when I want answers I am told there's nothing they can do I must pay the money.ans again on the 7 August 2023 at 21.48 I called head office again and was told there's nothing they can do I have to pay and ask them why and the answer was I have been paying very well in the last month's and thats why they decided to increase my spend limit and never got helped but got cut.im not happy coz I paid my monthly instalments which was agreed upon and the was no agreement about this so can mtn open my services coz dont remember signing for extra charges.