Stroller/car seat compatibility?

Alyssa 🍍 • August 2nd 2016 💟
We just bought a Britax stroller from Once Upon A Child and I was told by the employee that only Britax carseats can be used? Is this correct or is there an attachment I can get to use a different brand? Not a problem if we have to stick with Britax just curious. TIA :)