Problem with low-level firmware of telephone T21 E2

[protaganist]

Good day everyone,
i have a problem with low-level firmware of telephone T21 E2. the thing is in Russia this phone is sold only by local company (Mango office), and it has preset firmware which works only with certain VoIP provider.

When I try to install the firmware thru server TFTP the following bugs shows up:
1. 3CDaemon – Error received from peer: File too large
2. tftpd32 - Peer returns ERROR <File too large> -> aborting transfer

On the telephone display the following inscription shows up - Update failed (-6, 13)
All firmwares that are available for downloading (.rom) have size about 8 Mb.

Please help, what is the problem, how can I install normal-working firmware, which will work other then preset operator?
Windows 7x64