I can't answer for why your speed is still low, maybe call in to Telkom to let them explain. From 1 May for 3 months mine is higher automatically, no application needed, and I think someone in this thread also indicated their 10Mbps line is automatically running at 20Mbps.
I called in to the sales line and apparently as from tomorrow (15 May 2020) the introductory offer is available to new subscribers for 6 months. at R199 pm for naked ADSL at 4Mbps, and thereafter R329. Existing customers can get the R329 immediately, obviously by cancelling their phone line...