Airtime problem

This morning I went to buy airtime at a shop on my way to work, when I tried to load the airtime it failed a few times and I thought as I was driving I asked my colleague to try it but it failed too. And I got a message that I need to try the airtime again in 24hrs, then I called mtn customer care and I spoke to an agent to assist me to load my airtime. The agent asked me for the top-up number which I gave him and he said it was wrong then I gave him the airtime serial number which he said it was also wrong too. Now I am sitting with airtime that I cannot use and I am in need of making urgent calls to my clients which I can't do. Thanks to the super MTN and its opps. Maybe its time I consider moving to another network then. So many years sitting for **** service.