complaint in regards with fondi fone dt never work

Bought a fondi fone at russells only to find dt none of the network providers work?had try cellc,vodacom,mtn,8ta and evn telkom and still it ddnt wrk...2days later after iv tryd all netwrks i yhoght i had to return it as it is insured too...they took d fone at russells said they wll send it to fondi supplier,said i shdnt cum to d store bt should wait fr d supplier to call..after 36 days counting russells calls and tells me dt fondi says i should pay them R879 fr thm to fix it...now they say its actually broken ..d worse part is wasnt broken bt it had a netrwk fault..d fones whole cover was un removable bt i dnt knw y on earth they removed it ...i nyd hlp cz m still gna b paying fr ds fr d next 23 months and i dnt hav d fone cz they threatend if i dnt pay them they will return it broken i never asked thm to break d cover,plz help