Logo von AfA Arbeitsrecht für Arbeitnehmer

+75 % tracked leads through call tracking

Trichter Icon

+75 %

Tracked leads

User Icon

+170 %


Telefon Icon

+35 %


With the implementation of comprehensive call tracking, the number of tracked phone calls increased by 75%. At the same time, generated leads increased 1.7 times.

Our client

AfA Rechtsanwälte is one of the few specialized law firms in the field of labor law. With 25 attorneys, they exclusively advise employees, work councils, as well as executive employees and managing directors across more than five locations in Germany.

Initial situation

For measuring the success of online marketing campaigns, conversion data is essential. However, particularly with lead-based clients, these conversions at the macro-level are typically collected through form submissions or sent emails. Contrary to common belief, many users, especially when dealing with sensitive and advisory-intensive topics, still prefer to make phone calls. Since the threshold for making a call is often higher than submitting a form, the quality of leads also improves. Consequently, the conversion rate for calls is notably high – around 29% of callers become customers. Therefore, it is crucial to comprehensively track these phone calls.


The simplest but less data-reliable solution is measuring clicks on the <a href=”tel:....”> link. The problem with this approach is that it assumes users interact with only one device. Additionally, it cannot determine whether the call was successful. In reality, a phenomenon known as "media disruption" is often observed: users see the phone number on the website but then use their smartphones or landlines to manually dial the number. In such cases, the click trigger isn't activated at all. Hence, a more reliable solution is needed, one that provides more insights – comprehensive call tracking. This approach allows for both quantitative and qualitative evaluation of calls. Incoming calls can be enriched with valuable information from the customer journey, such as:

  • Channel 

  • Campaign

  • Keyword

Moreover, the call is registered as an event in Google Analytics or as a conversion in Google Ads.

Call tracking: setup & process 

The setup involves a code snippet ideally managed and integrated via Google Tag Manager. Through a "Search & Replace" function, the displayed phone number on the website is replaced by a number from a designated pool of numbers using JavaScript. As a result, each user receives a unique number and can be tracked. Depending on traffic, pools ranging from 10 to 1000 numbers are feasible. In a 1000-number pool, the last three digits are kept variable, for example: 0800 - 1234XXX. Calls to this call tracking number are then redirected to the actual customer's phone number. Additionally, service numbers like 0800 or regional area codes are possible. 

These numbers are registered with the Federal Network Agency and are owned by the customer, not Sunlab or the service provider. This remains the case even after termination of the service provider. The server processing the data is located in Germany. The script for this function must be linked to the cookie consent. If cookies are rejected, the script won't run, and the normal phone number will still be displayed.

Results and achievements

While the service does incur costs, call tracking brings significant benefits to online marketing beyond just insights:

  • The Google Ads algorithm has more data available

  • The data becomes more reliable

  • The actual lead value can be conveyed

Since the implementation of call tracking, the number of calls has steadily increased with a comparable budget. If only clicks on phone numbers were measured, about two-thirds of actual callers wouldn't be accounted for since users manually dial the numbers. Specifically, call volumes increased by about 35 % within a year (2020 vs. 2021). The following year, the success continued with call volumes rising by approximately 27 %.

Chart showing the development of call numbers for our client AfA Rechtsanwälte

Furthermore, Google Ads campaigns were consistently optimized based on call volume (primary conversion). Advertisements and keywords were developed, expanded, or discarded based on data. Our in-house bidding tool, Biddinglab's smart bidding algorithm, aligns seamlessly with the conversion data.

Thanks to Sunlab, we were able to continuously enhance our online visibility and web presence, leading to impressive results in client acquisition. Due to Sunlab's excellent guidance and support, we have been satisfied customers for years.”

Portrait von Larissa Scherer

Larissa Scherer

Management Assistant, AfA

More interesting case studies

Step into the future with Sunlab