Signal boosters can reportedly disrupt entire networks and now retail giant Amazon has been found selling unlicensed mobile phone signal boosters.

The US Federal Communications Commission (FCC) started tightly regulating signal boosters five years ago as the devices, if misconfigured or poorly manufactured, can knock out service for everyone who happen to be close by.

Today, all consumer signal boosters sold and marketed in the US must meet the agency’s strict technical standards. Doing so can get expensive, and many FCC-authorised boosters cost hundreds or even thousands of dollars.

E-commerce sites like Amazon offer cheaper options. The only problem is, they’re not always compliant, the Wired recently reported.

Amazon has been found selling signal boosters without US FCC licenses including those from Phonelex, MingColl, and Subroad and some marked as Amazon’s “Choice”.

The devices are not only unlikely to pass the registration process with carriers, but have caused service disruptions — more than one buyer has received complaints from carriers after their boosters interfered with cell towers. Call drops and disconnections are distinct possibilities, according to Engadget.

All of the six signal booster vendors spotted in the investigation appeared to be located in China with few if any contact details and were using bogus reviews to give the appearance of popularity.