MTN poor client service

Im Ipeleng Olifant .I bought a Samsung A30 phone and im not on contract.In these lockdown one has to constantly check on family.i bought airtime but when i punch the numbers it cnt go through informing me that i dnt have airtime.i called customer care but the voice message will ask me to punch my numbers but it keeps on saying one thing over and over again. I have an elderly mom who im to check everyday,i downloaded MTN App thinking it will assist but to my suprise im owing them R90.00 how i dnt know. I cnt even convert my airtime to make voice call their system say my package is nt allowing me for voice calls.