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My iPhone 6 will only get 3g and bad cellular, sometimes 4g but then it immediatly drops back to 3g, how can i fix this? Cellular works fine except for this issue.. it is kind of annoying considering that 3g is much slower than 4g. Thanks in advance!

Someone maybe able to correct me on this but the phone has multiple antenna`s for cellular, one built onto the charging port flex, and the others are built into the top and bottom of the phones back housing.