Please free me form this expensive arrangement

My husband took out a contract with Nashua Mobile where we used to take out cellphone and other gadget under one account for convinience. Unfortunately Nashua Mobile closed down and my handset was transferred to MTN. Since the transfer I have been wishing this 2 year period away, but I feel I should just let my feelings about this network be known. Never did I hear that one can purchase an airtime voucher and before you can even make a call your airtime is depleted (happened to me today). I load airtime, I see it on my balance, but when I do make a call I am told I have insufficient airtime to make a call. When I go to the MTN shop to enquire I am told there is nothing they can do I must call when it happens.When it happens and I call and am told I cannot be helped because I am not the account holder. What is worse the account holder does not use MTN and does not have the details of my problem, what must he call and say. There must be a way to get out of this arrangement because I really cannot afford it. The reason I chose this top-up option was to control my spend. What I am experiencing now in purely not achieving that result. <br> To me this is purely ********* and unacceptable.