It’s 2017, which means we’re long past the days when your phone should lock you in to one particular carrier. Unfortunately, Google doesn’t seem to agree.

A new report from Cellular Insights takes a deep dive into how the Google Pixel XL performs on different networks. According to their testing, 3x Carrier Aggregation — a feature that combines different LTE bands for blazing-fast speeds — doesn’t work on T-Mobile, but does on Verizon.

The end result will be slower speeds for T-Mobile users compared to Verizon, even if the two networks are totally equal in one place. It’s a handicap for T-Mobile, as most customers won’t know that it’s the phone causing the slowdown.

The reason for the lack of 3xCA on T-Mobile appears to be software related. 3xCA works just fine on Verizon, and Google advertises 3xCA as a feature for the Pixel XL. Cellular Insights explains the problem:

“Despite the device being fully unlocked and (at least initially) marketed in North America as Cat 9 capable, Google exercises the right to enable and disable not only LTE bands and CA combos on “per operator” basis, but capabilities and features as well, such as LTE Category and Higher Order Modulation. We simply can not rationalize the reason behind this decision, but it is hard to imagine that this was an accident, knowing that T-Mobile is one of the very first U.S. operators to rollout 3xCA, as well as one of the first operators globally to activate DL-256QAM, UL-64QAM, EVS, etc. We are hoping that one of the upcoming Google OTA updates will take care of T-Mobile specific carrier profile, allowing the Pixel XL to take the full advantage of the network.”

With your tinfoil hat on, there’s one obvious explanation for this behaviour: Verizon is the exclusive carrier retail partner for the Pixel and Pixel XL in the States. If you want a Pixel on T-Mobile, you’ll have to buy it outright unlocked from Google and get your own T-Mobile SIM. Hypothetically, there might be some agreement between Verizon and Google to only enable certain network features on Verizon, giving the network a sly upper hand.

Google did not immediately return a request for comment.