Designing a nuisance call blocking service for BT landlines

Product design case study

Problem: Customers receiving nuisance calls to their landline and need a blocking tool
My Role: Embedded UX designer
My approach: Led product team through 5 iterative design sprints
Deliverables: 5 interactive Axure prototypes
Customers: 25 qualitative usability tests
Results Month 1: 14,000 per week active users / 5,020 per week blacklisted numbers

BT Call Protect final design


BT Call Protect allows customers to block nuisance calls to their landline phone using a web app or their house phone’s touch tone keys. Users are able to blacklist numbers, set up do not disturb times, create VIP contacts and control international and premium calling. It was launched to combat PPI cold calling and other types of harassment of vulnerable customers.


As the embedded UX designer in the BT Landline product team I helped them with the following objectives:

  • Design a web app for customers to manage incoming calls to their landline phone
  • Reduce nuisance call complaints to customer support
  • Increase customer satisfaction and NPS

My contribution

I guided the product team through 5 iterative design sprints each of which had a day of usability testing.

Customer’s personal blacklist

Early testing showed us that customers expected to log in and see their blacklist first, despite the most common use case being blocking from their recent call list, so we made the blacklist the focus of the dashboard.

A high proportion of BT customers are 50+ with low-to-moderate computer confidence so we worked on interaction design patterns that were clear, self contained and hand held them through task completion.

We displayed relevant actions on each phone number in the recent call list so customers learnt that withheld numbers can still be block because BT has the number but hides it, while unavailable numbers are unknown to BT. Any known number can also be added to a VIP list which can be set to bypass any do not disturb settings.

Do not disturb feature

The do not disturb feature stopped the customer’s landline ringing during certain hours on certain days, and we learnt that some VIPs are more important than others so we let customers choose which of them respected the do not disturb settings.

Turning blacklisting on and off

In the settings we needed to make a clear distinction between the customer’s personal blacklist that they curate and the centralised BT blacklist which is created and managed by algorithms that analyse call behaviour at scale.

Running count of blacklists and diverted calls

Because a blacklisted number diverts silently to a junk voicemail the service was invisible to customers when in action so we displayed a running count of diverted calls in the last 30 days to keep showing the value being delivered. We hoped that this would contribute to a rise in customer satisfaction and NPS.

Final thoughts

BT Call Protect launched in 2017 and in the first couple of months there were 14,000 per week active users and 5,020 per week blacklisted numbers.

This was the first product I worked on in my first few weeks at BT and I was initially skeptical as to its need until I learnt just how much of the older population in the UK rely on landlines as their only form of communication and how much PPI cold calling was disrupting their lives.

There was also a moment in the usability testing when a divorcee stopped in mid sentence and stayed quiet for about a minute while she realised how much she needed the product after she divorced her abusive husband who continued to harass her by phone.

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