MLG UNABLE TO GET PERMISSION TO DEVIATE TSTMS. FREQ CONGESTION; COM STEPPED ON. ENTERS WX; ALTDEV.

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DEPARTING ORD; CLBING TO 13000 FT; DEP CTLR WOULD NOT ALLOW ANY FLTS TO DEVIATE FROM DEP COURSE DUE TO ORD ARRS. DEV WOULD BE NECESSARY BY 20 MI BECAUSE A LINE OF TSTMS WERE ON THE DEP COURSE. CTLR SAID HE WOULD HAVE A FREQ CHANGE SHORTLY AND CTR WOULD ALLOW US TO DEVIATE AROUND THE STORMS. WHEN MY ACFT WAS ABOUT 10 MI FROM STORMS A FREQ CHANGE WAS GIVEN BUT THE XMISSION WAS 'STEPPED ON' BY ANOTHER ACFT. CTLR DID NOT WAIT FOR A READBACK AND CONTINUED TO ISSUE INSTRUCTIONS TO OTHER DEPS. BY THE TIME WE WERE ABLE TO CONFIRM THE FREQ CHANGE WAS FOR US; AND THE FREQ; WE WERE AT THE EDGE OF THE TSTM. CTR CLRED US DIRECT TO ELX AND APPROVED OUR REQUEST TO DEVIATE N. AS I STARTED THE TURN N AND BEGAN TO LEVEL OFF AT 13000 FT; WE ENTERED INTO HVY RAINSHOWERS; LIGHT HAIL; AND MODERATE TURB. ACFT ALT CLBED TO 13380 FT. IN CORRECTING BACK TO ALT; ACFT DSNDED TO 12750 FT AND THEN LEVELED OFF AT 13000 FT WHILE STILL IN THE EDGE OF THE TSTM. WE THEN EXITED THE STORM AND SUCCESSFULLY MANAGED TO DEVIATE AROUND THE REMAINDER OF THE LINE. NOT FOLLOWING STANDARD COM AND BEING PREPARED FOR ALTERNATE ROUTING BY DEP CTL CAUSED MY FLT TO GET DANGEROUSLY CLOSE TO A TSTM AND AFFORDED US VERY LITTLE TIME TO AVOID A DANGEROUS SIT.