Inbound data roaming Vodacom

[Pieter Wiid]

I am with Standard Bank Mobile, which nominally uses the CellC network, with roaming on Vodacom or MTN "whichever signal is stongest" as per SMB helpdesk. Since the CellC reception is so dismal in my area, I permanently roam on Vodacom; can't roam on MTN at all "not allowed". When roaming on Vodacom, I can't get data connection better than Edge, in spite of having set my connection to LTE/3G/2G auto-connect, and data roaming on.
SB Mobile are completely clueless. Does anybody have ideas on how to get LTE while roaming on Vodacom?