Vodacom ripping me off!

I signed up for new contract in December 2019 for a business 300 gig lte line with speeds of up to 25mbps .For the past 2 months I have been experiencing speeds of 4mbps and lower.I contacted the call centre I was given a reference and was told the matter was resolved after 3 weeks.i went to the Vodacom Bluff store where the contract was taken out and informed them there was no difference in speed.The manager did assist us by sending an email to the person concerned.I still have got no response to date.I have been to the store on numerous occasions and sent many emails to no avail.I am currently paying R998 for a contract that is of no use to me.This service is unacceptable.