Narrowband-Internet of Things (NB-IoT) is a relatively new Low PowerWide Area Network (LPWAN) technology used to implement large-scale IoT applications. The economic viability of most applications depends on a long battery life of deployed devices ((1) over tilde0 years). In this paper, we document two interference attacks on the NB-IoT communication link that lead to a battery depletion in devices. These attacks can be carried out without disruption of data delivery and are therefore hard to detect. We describe a Matlab based simulation environment that can be used to investigate interference on NB-IoT communication, and we then use this environment to study the two attacks. For example, we show that battery lifetime can be reduced from 17 years to as low as four months.