Device locked for Vodacom SIM only

Good day

I have tried speaking to Vodacom telephonically and went to Woodlands store.

Bought an android phone in Ackerman's just over 1and half years ago. I was told that the device is locked to Vodacom Sim Only for 12months, then I will be able to unlock device to use other service providers.

I need assistance as no one at Vodacom seems to get it right and they said it’s not possible. I do not feel this is correct or fair and how can I not be able to use other service providers?