Yes, technically you pay for all MobileX services in advance, although it can occur at different time periods. MobileX doesn’t offer set plans per se, although to successfully activate the service, payment will be required. You have two options:
1) You can go through the learning period phase which accurately gives you a personalized GB amount. This option has you pay after for the GBs recommended by MobileX.
2) You can set your own data allotment in advance, which requires immediate payment. This option has you pay before for the GBs.
We recommend you go through the learning period experience to know your customized GB amount.