Unknown Content Charges

I have been trying for ages to find out who is responsible for content changes on our guard's phone. Afrihost say that it is MTN's fault and MTN say there is nothing loaded, but there it is:

27/02/2019 - 01:12 Content 'Service rent charge' from SDP CMO HUAWEI TECH AFR R 0.25 02/03/2019 - 01:40 Content 'Service rent charge' from SDP CMO HUAWEI TECH AFR R 0.50 20/02/2019 - 00:40 Content 'Service rent charge' from SDP CMO HUAWEI TECH AFR R 0.50 13/02/2019 - 04:14 Content 'Service rent charge' from SDP CMO HUAWEI TECH AFR R 0.50 06/02/2019 - 01:05 Content 'Service rent charge' from SDP CMO HUAWEI TECH AFR R 0.50

50 cents every week for months. How to I get rid of this or find out who is responsible.

Thank you.