I did have a problem with servicing the oxygen contcentrator several times. But the worst was the emergency oxygen stand by change. The first time I called 8 times every day and they was playing the sell game. The new one is just started this Monday 12-16-2019 and till going on today 12-19-2019 I called even today at least today they promise me I will get my emergency oxygen tank refiled. 4 days 4 call what they announce will be recorded. I just called my pulmonologist to fined me a other company