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Old T-Mobile SCH-T399 & DPH-151

I use a DPH-151 in a vacation condo over the winter months. My daughter-in-laws T-Mobile branded SCH-T399 will not connect to it. She uses the phone normally as part of our AT&T Mobile Share Value Plan. Of the five phones in the plan, including three iPhones and a Lumia 640, that phone is the only one that will not connect to the Microcell.

Previously I added the number to the authorized list in the Microcell and had her power off then power on the phone when she arrived.

Are there any logs accessible that I could look at to give me any clue as to what is happening?

Is that phone simply not compatible?

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OttoPylot

ACE - Expert

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24.2K Messages

8 years ago

The MicroCell model number has no bearing on the connectivity because they all use AT&T Mobility. My guess is that because the older phone is branded as a T-Mobile phone, that the IMSI device coding is not recognized on the AT&T network. The IMSI number is converted by AT&T’s IT Department to a phone number. But AT&T doesn’t have a list of all of the possible IMSI numbers worldwide because that would be very expensive to maintain. The MicroCell is an IMSI based system which is how it ties into the AT&T network and forces conversion to actual numbers. The coding is usually embedded in the SIM card. This is not to be confused with the IMEI number which is the AT&T registration number and probably the reason why the phone can connect when outside of the MicroCell range.

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