Debian 10 trouble connecting to AT&T LTE

i am trying to get my laptop to connect to my LTE service from AT&T, but i am having difficulties getting it to use LTE.
some googling showed that the name of AT&T’s LTE apn is “phone”
so i issued the command:
mmcli -m 0 --simple-connect=“apn=phone”
and it responds with “successfully connected the modem”
i use the command “mmcli -m 0” to verify that it connected and it shows this: ` --------------------------
General | dbus path: /org/freedesktop/ModemManager1/Modem/0
| device id: [redacted]

Hardware | manufacturer: Sierra Wireless, Incorporated
| model: Dell Wireless 5808 Gobi? 4G LTE Mobile Broadband Card
| revision: SWI9X15C_01.08.16.05
| h/w revision: MC7355
| supported: gsm-umts, lte
| cdma-evdo, lte
| lte
| cdma-evdo, gsm-umts, lte
| current: cdma-evdo, gsm-umts, lte
| equipment id: [redacted]

System | device: /sys/devices/pci0000:00/0000:00:14.0/usb2/2-10
| drivers: cdc_mbim
| plugin: Dell
| primary port: cdc-wdm0
| ports: wwp0s20u10c2i12 (net), cdc-wdm0 (mbim)

Numbers | own: [redacted]

Status | unlock retries: sim-pin2 (3)
| state: connected
| power state: on
| access tech: hsdpa, hsupa
| signal quality: 29% (recent)

Modes | supported: allowed: 2g; preferred: none
| allowed: 3g; preferred: none
| allowed: 2g, 3g; preferred: 3g
| allowed: 2g, 3g; preferred: 2g
| allowed: 2g, 4g; preferred: 4g
| allowed: 2g, 4g; preferred: 2g
| allowed: 3g, 4g; preferred: 3g
| allowed: 3g, 4g; preferred: 4g
| allowed: 2g, 3g, 4g; preferred: 4g
| allowed: 2g, 3g, 4g; preferred: 3g
| allowed: 2g, 3g, 4g; preferred: 2g
| current: allowed: 2g, 3g, 4g; preferred: 2g

Bands | supported: egsm, dcs, pcs, g850, utran-1, utran-4, utran-5, utran-8,
| utran-2, eutran-2, eutran-4, eutran-5, eutran-13, eutran-17,
| eutran-25, cdma-bc0, cdma-bc1, cdma-bc10
| current: egsm, dcs, pcs, g850, utran-1, utran-5, utran-8, utran-2,
| eutran-13, cdma-bc0, cdma-bc1

IP | supported: ipv4, ipv6, ipv4v6

3GPP | imei: [redacted]
| enabled locks: fixed-dialing, ph-fsim, net-pers, net-sub-pers,
| provider-pers, corp-pers
| operator id: 310410
| operator name: AT&T
| registration: home

SIM | dbus path: /org/freedesktop/ModemManager1/SIM/0

Bearer | dbus path: /org/freedesktop/ModemManager1/Bearer/5
`

under the status section, it shows access tech is hsdpa, hsupa. not LTE. and the horrible speeds (around 100Kb/s) are about that one would expect from a 3g connection.
what am i doing wrong here?