wifi conflict with 3g

Dear Sir;
My phone is:
Huawei GRA-L09
Build number: GRA-L09V100R001C900B110
IMEI:357996024849281
SN: U5V3A914B1410004
I have a problem as follows:
* The phone can't make or receive calls when wifi & 3g is active together in the same time..!
* if I turn wifi off and leave 3g on it works good.
* if I choose network only 2g and leave wifi on also work good.
Please help me solve this problem.
Thanks a lot.