Endless sms'on my Telkom landline

Please help. I keep receiving sms' on my Telkom landline from *** informing me that my data bundle has been depleted and without a data bundle out of bundle rates apply, to purchase a data bundle I must dial last risk 100?. I've contacted Telkom via HelloPeter and they inform me that the calls are not coming from them so there's nothing they can do to block these calls. I receive up to 13 of these sms' one after another. This is most annoying. My Telkom data is capped and I NEVER go over the allocated data amount. I do get data each month from Vodacom for my pc and 2 tablets but never use anywhere near the amount of data that I receive. Perhaps Vodacom can assist and see if these calls are coming from them? Thank you.