Other fillers in the same area as the filler

I got a domestic filler on my chin and
 Perfecta on my nose and forehead, but
 
it's been 3-4 months since I got my chin filled, and since it's domestic, it feels like it's all fallen off, so
 I'm thinking of getting it imported, but
 
when I go to another hospital to get skin care,
 they asked if there was any filler left in my chin
 , and they said there was
 , so I should get it with the domestic filler I got before,
 and they said it doesn't matter. The stylist said that I can get a different one
 even if I still have the domestic filler I got before,
 but as far as I know, the side effects get worse if you get a different filler in the same area.
 Did I misunderstand something or is this the hospital's sales pitch?