No customer service

I've been struggling since 20 / 21 Nov last year to get a R250 pre-paid landline voucher validated or refunded but to no avail. Voucher no. 1 ********** 7 ********** , serial no. 1 ********** 4 ********** 01. Ref S9CJGRKTD. I bought the pre-paid voucher for my parent's home phone via FNB's mobile banking app & apparently there was problems with the voucher numbers from Telkom because the voucher number was invalid & I had to contact Telkom directly for it to be fixed. I've called their call centre numerous times & logged complaints on their customer service portal but still nothing. They do not give ref# no.'s when you call so every time you log the inquiry it just starts the process over again. I've been told that it will take about 1-2 weeks to resolve & someone will call the landline for which the voucher was bought to resolve the problem but to date no one has called. I'm really disappointed in the service Telkom provides & find it appalling that things can drag on forever.