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Case Study - Insights driven testing

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Goal
We believed that introducing a plan calculator on the SIM page would help users filter according to preference.


Expected Outcome:

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  • Users quickly narrow down plans based on plan length, data amount, and plan type.
     

  • Increased add-to-basket rates and SIMO orders.

Problem Statement

On the VodafoneThree SIM Only page, multiple named tariffs were displayed in a single, long list.

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  • User confusion: Users struggled to understand the differences between plans.

  • Difficulty filtering: The flat list format did not allow users to narrow down plans based on their needs.

  • Overwhelming experience: Too many options presented at once created decision fatigue.

Comprehensive testing of personalisation and multivariate factors across the entire Three website. 

What does success look like

Reached 'Significance' within 3 days of conducing an A/B test on the SIM Only calculator

11% increase in customers purchasing a SIM only plan within the  Experience B group

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Launched within BAU within a 6 week turn around and continually optimised

Documentation and Communication

  • Documentation
    Keep detailed records of your design decisions, research findings, and user testing results.

  • Collaboration
    Communicate effectively with cross-functional teams, including developers, product managers, and stakeholders, to ensure a shared understanding of the design goals.

Process

Research & Insights

Analytics & Decibel recordings revealed users scrolling extensively but rarely compared plans
 

1:1 user testing & verbatim feedback users said things like:
 

“I don’t know which plan is best for me.”
“It’s hard to compare all these options at once.”

 

Users needed a guided, personalised way to find the right plan without scanning all 24+ tariffs.

Solution

To address the limitations of Experience A, I analysed the existing user journey and identified key areas for improvement. Rather than iterating on the current solution, I explored alternative directions by designing two concept concepts: Experience B and Experience C.

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These mock-ups acted as exploratory tools to visualise different approaches, test assumptions, and demonstrate how the experience could better meet user needs. I shared both concepts with the wider team to facilitate discussion around feasibility, technical constraints, and audience fit.
 

This collaborative evaluation helped us align on a clear, user-centred direction that balanced design intent, technical capability, and business goals, informing the next phase of development.
 

Dynamic plan calculator redesign:
 

  • Users select preferences; only matching plans are displayed

  • Interactive filters: Adjusting filters updates results in real-time for easy comparison

  • Simplified choice: One optimal plan shown at a time, reducing cognitive load

  • Improved clarity & usability: Users can make decisions faster without scrolling

Evaluate

The chosen concept is built into a testable interface and rolled out to 50% of users over a 3 week period or until significance is hit.

Expected Outcome:

  • Quickly filter by plan length, data, and plan type

  • Increase add-to-basket rates and SIMO orders
     

Success Criteria:

  • +10% add-to-basket rate

  • +7.5% SIMO orders

Results

Experience B
15.3% of share of visitors adding SIM to basket
10.2% in CSIM conversion rate (significant)

Experience C
9.4% of share of visitors adding SIM to basket​
4.8% in CSIM conversion rate (significant)

Experience B a winner, this was rolled out into BAU experience.

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