A controlling method for a wireless communication device is provided. The controlling method for the wireless communication device includes: attaching a first Universal Subscriber Identity Module (USIM) to a Long-Term Evolution (LTE) network; determining whether a second USIM is camped on the LTE network; detecting whether a paging collision is happened, if the second USIM is camped on the LTE network; generating a requested International Mobile Subscriber Identity (IMSI) offset for the second USIM, if the paging collision is happened, wherein the requested IMSI offset is 1 or min(T, nB)−1, T is a default paging period and nB is a number of paging occurrences within the default paging period; transmitting an attach request with the requested IMSI offset to the LTE network for the second USIM; receiving a negotiated IMSI offset from the LTE network; and attaching the second USIM to the LTE network with the negotiated IMSI offset.