Poor connection while on a network connection

I have been having terrible connection for the last 8 months while I am on a network connection. My contract is on a business package and we have done a sim swop, put my sim card into a different handset, reset network settings, reset all settings, wiped the phone completely and restarted from a backup and nothing works. Switched to airplane mode, switched to 4G, changed internet settings etc etc. I have called in a few times to speak to the Vodacom customer care consultants and none have been able to resolve my query. Basically, I struggle to connect to the internet, I cannot send or receive photos on platforms such as whatsapp or facebook, and I often get the no access to internet sites messages (unrestricted sites). These issues are non-existent while I am on a WIFI connection, only have issues on network connection. I have been waiting for over 2 weeks for the technical department of Vodacom to get back to me with an answer. What is worse is that this problem is intermittent in some days and completely broken in other weeks (as it is now). The problem also occurs no matter where I am, home, work, Johannesburg, KZN, etc. Can someone please help me!!! I basically have a handset that I can only use when I am on WIFI which is rather pointless and my company pays a lot of money to Vodacom every month to have this issue. I am using an iPhone 7.