The purchase was announced after an agreement was reached with TeamTalk Limited to buy the remaining 30 per cent stake in BayCity Communications Limited, trading as Farmside, for $3 million.
In June 2017, Vodafone bought 70 per cent of Farmside for $10m.
As a part of that transaction, Vodafone retained the right to acquire the remaining 30 per cent for $3m at any time within a three-year period.
Farmside general manager Jason Sharp said it would be business as usual at the Timaru operation which employs about 47 people, tasked with engaging 14,000 customers nationwide, while fielding about 10,000 phone calls a month.
"It's business as usual for our customers and our team here in Timaru, we can continue to do what we love, which is connecting rural New Zealanders.
"This investment is a significant opportunity to enhance services and products available to our customers.
"It also drives home the importance of the Farmside brand, its value and level of trust within the rural community is significant, which Vodafone has recognised.".
Farmside would operate as a separate entity to Vodafone, he said.
"This means that Farmside will continue to run as it's own business.
"Vodafone has no plans to make any major changes to the business at this stage.
"Farmside will remain in Timaru with its full existing staff and expects to recruit a small number of staff in the coming months."
Sharp said it was "a very positive development..."
"It means our customers are able to get the best of both worlds; continuing to enjoy industry leading customer service and rural connectivity knowledge from our Timaru team but also, being able to take advantage of an enhanced products and services range that will eventually come with this change in ownership.
Vodafone chief executive Russell Stanners said the investment further deepened their commitment to rural communities.
"With Farmside now firmly a part of the Vodafone family, we can continue to deliver better outcomes for these communities and increase our presence in the rural broadband market".
The ownership change becomes effective from midnight May 31.