Sprint phones supporting the carrier’s new Spark network don’t support phone calls and data-use simultaneously, according to Consumer Reports.

Sprint Spark devices use eCSFB technology which enables single radio functionality in the handset, allowing Sprint to use multiple CDMA and LTE spectrum bands. But “simultaneous voice and LTE is not supported on new Sprint Spark devices,” Sprint confirmed to Phonescoop.

Sprint did not immediately respond to an inquiry regarding the matter.

Other LTE phones, like the Samsung Galaxy S4, in Sprint’s portfolio don’t have issue with handling voice and data functions at the same time. But, as Consumer Reports pointed out, Sprint iPhones have never been able to use voice and data simultaneously.

Consumer Reports pointed to GPS as a particular point of concern, noting that Sprint Spark devices will drop the GPS signal when a call is received. But Consumer Reports did praise the HD Voice capability included with Sprint Spark handsets.

Sprint Spark is the carrier’s recently deployed tri-band LTE, taking advantage of Sprint’s newly acquired licenses in 2.5 GHz to boost speed and capacity. Sprint has promised LTE downlink speeds approaching 150-180 Mbps in the next two years. Spark is already up and running in 18 cities and Sprint plans to have it deployed in 100 within the next three years.

Possibly coming sooner is Sprint’s nationwide HD Voice. Sprint this week sent out press invitations for an event April 29, promising attendees a chance to “hear it for yourself.”