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The Fido Dollars can not be used to pay your bill. Since the Fido Dollars program was ended we can not redeem the Fido Dollars through any self-serve methods, a Fido representative will have to assist with the redemption.
This the the redemption terms taken from FidoREWARDS Program Terms and Conditions section 8 here.
Redemption of available FidoDollars. FidoREWARDS participants can redeem their available FidoDOLLARS on fido.ca/rewards, in certain Fido stores or by calling 1 888 481-FIDO (3436). The FidoDOLLARS available can only be used toward the purchase of Fido phones (other than smartphones, unless a participant subscribes to a data add-on with a commitment period or to prepaid service) mobile internet devices (with a subscription to a data add-on with a commitment period) or the following add-on services: Name Display, Call Display, Call Forwarding, WhoCalledTM, #AUTO, Expanded Network, Suburban zone, text messaging, international text messaging, picture and video messaging, Additional Minutes (anytime local calls), Fido to Fido Anywhere in Canada, Canada/U.S. Long-Distance, International Long-Distance, U.S. roaming and Happy Hour, in each case, from among those available at the time of FidoDOLLARS redemption, or toward $20 increments of prepaid airtime. Each FidoDOLLARS point corresponds to one (1) dollar applicable to the regular price in effect at the time of FidoDOLLARS redemption, including applicable taxes, except for taxes applicable to add-on services which cannot be paid using FidoDOLLARS. FidoDOLLARS have no monetary value and cannot be exchanged for cash. FidoDOLLARS can only be used in accordance with these terms and conditions and participants cannot sell, buy, give, transfer or otherwise dispose of their FidoDOLLARS without Fido's prior written consent. Only the account holder or any authorized user designated by the account holder may redeem available FidoDOLLARS or otherwise manage the FidoDOLLARS associated with that account. Fido may validate the identity of any account holder or authorized user before allowing them to redeem any FidoDOLLARS.