T-Mobile US (TMUS): Trim FY26 ARPA and Service Revenue, but Medium-Term Growth Profile Keeps Us Overweight; PT to $260

J.P. Morgan updates its T-Mobile US (TMUS) estimates ahead of 3Q results. We maintain our 3Q postpaid account net adds forecast of 260k but lower our 3Q wireless service revenue estimate 0.2% to $19.30b (in line with guidance of $19.30b), reflecting reduced postpaid revenue of $16.14b on lower ARPA of $154.50 (+3.4% y/y), with prepaid and wholesale unchanged. As a result, we trim 3Q core EBITDA 0.1% to $9.41b (vs. guidance of $9.4b). For FY26, we reduce total service revenue to $76.79b (vs. guidance of $77b) on the flow-through of lower ARPA growth of 3.3%, which drives postpaid service revenue of $64.07b. We also lower 2026 core EBITDA modestly to $37.35b (the midpoint of the $37.1-37.5b range) and now model FCF of $18.60b on capex of $10.02b. We remain Overweight T-Mobile but trim our December 2027 price target to $260 (from $275) on lower postpaid service revenue growth. Our updated target implies 12.0x 2028E FCF/share, versus 8.7x 2027E FCF/share today. Our Dec '27 price target is