"It's better to have a big shock, but well done and well prepared with all the risks anticipated and analysed. And then the system adapts itself because of the nature of the change and the volume of the task of the people - they can deal with anything after that.
"The important thing is to get that first success, and then it becomes like a very strong light to everybody, who start to feel part of the decision-making process."
EE was ranked by The Sunday Times this year at number 18 in its list of best big companies to work for, and Karonis was particular proud that his own department is regarded very highly internally at the company.
"We are one of the top 25 workplaces in the UK for employee satisfaction," he said.
"And the IT people feel that they are essential in the productivity of the company. IT is at the top of the company's internal score, so they feel they are driving the company and are involved in the decision-making which makes me proud.
"So I have experts and partners and IT teams that work with users and know the business, and they can negotiate a solution that actually fits in with the business objectives.
"We have mixed working groups working with other departments like customer operations and finance and we try to ensure that we listen carefully to them.
"This engagement level is the maturity of the company, and at the top there is really only one team at the executive level. We all work for the same objectives, and my objective is creating value for the company."
As part of the merger and transformation, Karonis was able to slim down the size of the operation at EE, ditching data centres and moving their infrastructure to the cloud, as well as slashing the number of applications the company uses.
"We built an on-site data centre, a private cloud if you like. We had a current mode of operation with a host of data centres, but we wanted to get to a future mode of operation which is about dynamic computing and bundled security.
"We saved about 25% of our operational expenditure, around £50 million, moving our infrastructure to the cloud. For me, innovation is driving this, making us a flexible, healthy and scalable company.
"IT liberated costs in the merger which we could quickly reinject in other parts of the company."
Karonis also explained the savings the organisation was able to make to aligning the areas of the business which have extremely similar requirements.
"Overall, if you look at big telcos like us, we have our large call centres and stores and corporate side which have reasonably close requirements so its most effective to have some options for laptops or similar devices for corporate employees.
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