remax power bank

bought a remax power bank via mail order on a "so called special" - within 7days reported that the unit was not fully charging - and requested for an immediate replacement.the response - they will collect the unit,have tested and then replace - however if they find the unit working ,i would have to pay for the return costs.this units takes days to charge and has not reached the 100% mark. Sadly it seems that this unit was not properly tested .i am sitting with a faulty unit that comes with all sorts of issues with regards to any guarantee(s) - not impressed