Rewind to mid-2014 and Callander was running CallPlus - the umbrella company for the telco businesses predominantly owned by former husband and wife Malcolm Dick and Annette Presley - as it snapped up rival ISP Orcon.
The rationale was not just that Orcon was a good operation, which provided significant scale when added to the firm's existing Slingshot, CallPlus and Flip brands, but it was also a defensive play, ensuring the asset didn't fall into the hands of a rival, says Callander.
"For the first time we acquired a business that had a lot of staff, had capability, but also had a lot of very similar capability.
"The challenge we had when you go through that, you're buying your competitor so you have a lot of healthy tension and a lot of healthy, different views on what's the right way to do things.
"Where I think we managed the process very well was we were very clear on our communications around valuing the brand, valuing what the team had done over the last 10 years or so and that they had built up one of the best loved brands in the New Zealand market at the time."
While the geek-centric Orcon sat nicely alongside the mass-market Slingshot and budget-friendly Flip, consolidation was needed to reduce operational double-ups.
What helped was clearly articulating a shared goal to snaffle 25 per cent market share - the combined business currently sits at about 14 per cent, with more than $300 million in turnover - and explaining the benefits and rationale behind tough business decisions, he says.
"We had a firm direction on what we wanted to achieve, we had a structure we wanted to move to and we controlled the pace at which everything happened, so it was a good process.
"I think we got most things right.
"The Orcon team have come on board and if you walk around this business today, while the passion for the Orcon brand is alive and the passion for the Slingshot brand is alive, there is a wider passion, which is to connect one in four Kiwi homes to those brands."
The moment we start thinking we're a $4 billion company, we'll start losing the essence of what's made this company a success ...
Less than a year after adding Orcon to the line-up, the whole business was bought by Australian telco M2 Group for $250 million.
Callander says the sale by the founders, after almost 20 years, came as a shock to staff who viewed it as a family business.
"One of the biggest aspects we had with being bought by M2 is, how do we retain that level of passion in the business with a publicly-listed Australian telco?
"And there's no easy answer to that question but to me, one big part of it is about consistency, so the best thing about maintaining positive change and change management is consistency."
Callander is still the boss, the leadership team is still in the business, none of the brands have changed and the vision is still the same.
Part of that is down to M2's method of operation.
CallPlus was acquisition number 24 for M2, a business that runs as an "employment brand" with none of its acquisitions trading under the M2 banner.
After an early restructure, CallPlus was at liberty to keep doing what worked, but could call on M2 for help and the benefits a big organisation can bring.
"The reason that change was successful is we maintained consistency, we communicated very clearly to all our staff, we treated them all very respectfully through the process and we didn't change our vision and what we're about in this market."
The merger between M2 and Vocus Communications, an Australasian network and data centre operator, in September last year, was easier having been through the previous two deals, says Callander, but it was still change and people don't like change.
"It's still hard to get change right because you still have different people, you still have different views, you've got two network teams so you do actually have to navigate through a process that gets the best outcome for the shareholders and the staff, which we're still going through."
It's created a fully integrated business of 650 staff that puts it on an equal footing with its bigger rivals, but one which needs to preserve its challenger brand DNA, he says.
"The moment we start thinking we're a $4 billion company, we'll start losing the essence of what's made this company a success in the New Zealand market in particular." Callander, who says he thought he was "quite busy" selling $16.95 dial-up connections when he joined Slingshot more than a decade ago, has had his fair share of sleepless nights working through the deals.
While it's hard to switch off when change is afoot, he is still passionate about the business and its journey.
"As soon as I lose that and I'm lying awake at night for the wrong reasons that's when it'll be a clear sign that it's time to go."
