That's a lot of lines. Most units that have come up before only support a couple of lines (each line requires it's own SIM of course). You may have to go with multiple units.
There are several devices like that (bluetel, its, etc.), they either support an ISDN PRI connections (upto 120 channels) and/or SIP trunks as interface to the PBX. The problem is the price of the device - a 32-channel gateway used to be over € 15,000.-
I got a bunch of gsmgateways for sale.
1x 2n Bluestar 10 gsm PRI / New price: 16 000 EUR / My price: 2 000 EUR (Never used, new in box)
1x 2n Voiceblue 4 gsm VOIP / New price: 1 800 EUR / My price: 500 EUR (Used for 1 year)
6x Portech MV-372 2 gsm VOIP / New price: 300 EUR / My price: 150 EUR (Used for 1 year)
All have been running on 3cx, 20 users (the 3cx licens is also for sale) exept the 10 gsm gateway above.